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NCAA bans player for accepting help while homeless. | 0non-cybersec
| Reddit |
Logical reads different when accessing the same LOB data. <p>Here are three simple tests that read the same data, yet report very different logical reads:</p>
<h3>Setup</h3>
<p>The following script creates a test table with 100 identical rows, each containing an <em>xml</em> column with enough data to ensure it is stored off row. In my test database, the length of the <em>xml</em> generated is 20,204 bytes for each row.</p>
<pre><code>-- Conditional drop
IF OBJECT_ID(N'dbo.XMLTest', N'U') IS NOT NULL
DROP TABLE dbo.XMLTest;
GO
-- Create test table
CREATE TABLE dbo.XMLTest
(
ID integer IDENTITY PRIMARY KEY,
X xml NULL
);
GO
-- Add 100 wide xml rows
DECLARE @X xml;
SET @X =
(
SELECT TOP (100) *
FROM sys.columns AS C
FOR XML
PATH ('row'),
ROOT ('root'),
TYPE
);
INSERT dbo.XMLTest
(X)
SELECT TOP (100)
@X
FROM sys.columns AS C;
-- Flush dirty buffers
CHECKPOINT;
</code></pre>
<h3>Tests</h3>
<p>The following three tests read the <em>xml</em> column with:</p>
<ol>
<li>A plain <code>SELECT</code> statement</li>
<li>Assigning the <em>xml</em> to a variable</li>
<li>Using <code>SELECT INTO</code> to create a temporary table</li>
</ol>
<pre><code>-- No row count messages or graphical plan
-- Show I/O statistics
SET NOCOUNT ON;
SET STATISTICS XML OFF;
SET STATISTICS IO ON;
GO
PRINT CHAR(10) + '=== Plain SELECT ===='
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;
SELECT XT.X
FROM dbo.XMLTest AS XT;
GO
PRINT CHAR(10) + '=== Assign to a variable ===='
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;
DECLARE @X xml;
SELECT
@X = XT.X
FROM dbo.XMLTest AS XT;
GO
PRINT CHAR(10) + '=== SELECT INTO ===='
IF OBJECT_ID(N'tempdb..#T', N'U') IS NOT NULL
DROP TABLE #T;
DBCC DROPCLEANBUFFERS WITH NO_INFOMSGS;
SELECT
XT.X
INTO #T
FROM dbo.XMLTest AS XT
GO
SET STATISTICS IO OFF;
</code></pre>
<h3>Results</h3>
<p>The output is:</p>
<pre>
=== Plain SELECT ====
Table 'XMLTest'. Scan count 1, logical reads 3, physical reads 1, read-ahead reads 0,
<b>lob logical reads 795, lob physical reads 37, lob read-ahead reads 796.</b>
=== Assign to a variable ====
Table 'XMLTest'. Scan count 1, logical reads 3, physical reads 1, read-ahead reads 0,
<b>lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.</b>
=== SELECT INTO ====
Table 'XMLTest'. Scan count 1, logical reads 3, physical reads 1, read-ahead reads 0,
<b>lob logical reads 300, lob physical reads 37, lob read-ahead reads 400.</b>
</pre>
<h3>Questions</h3>
<ul>
<li>Why are the LOB reads so different?</li>
<li>Surely the exact same data was read in each test?</li>
</ul>
| 0non-cybersec
| Stackexchange |
What happens when modifying Gemfile.lock directly?. <p>Since the second time of <code>bundle install</code> execution, dependencies are loaded from Gemfile.lock as long as Gemfile isn't changed.</p>
<p>But I wonder how detection of changes is made between those two files.</p>
<p>For instance, if I'm adding a new dependency directly into Gemfile.lock without adding it into Gemfile (as opposed to the best practice since Gemfile.lock is auto-generated from Gemfile), would a <code>bundle install</code> consider Gemfile as changed ?</p>
<p>Indeed, does <code>bundle install</code> process compares the whole Gemfile and Gemfile.lock trees in order to detect changes? </p>
<p>If it is, even if I'm adding a dependency directly to Gemfile.lock, Gemfile would be detected as changed (since different) and would re-erase Gemfile.lock (so losing the added dependency...) </p>
<p>What is the process of <code>bundle install</code> since the launch for the second time ?</p>
<p>To be more clear, my question is:</p>
<p>Are changes based only from Gemfile ? That means bundler would keep a Gemfile snapshot of every <code>bundle install</code> execution number N and merely compares it to the <code>bundle install</code> execution N+1 ?</p>
<p>Or no snapshots are created in bundler memory and bundler makes a comparison with Gemfile.lock each time to detect if Gemfile must be considered as changed.</p>
| 0non-cybersec
| Stackexchange |
Android remove border hover from FloatActionbutton. <p><a href="https://i.stack.imgur.com/o4EXU.png" rel="nofollow noreferrer">current situation</a></p>
<p>So as you can see on the picture there is a shadow on the border of my button. Is there a way to remove the shadow so that that the color of the button corresponds with the color of my action bar. right know it looks ugly because you can see the shadow. This is my code:</p>
<pre><code><?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
>
<TableRow
android:gravity="end">
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="@+id/logInButton"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:borderWidth="0dp"
app:backgroundTint="@color/faviconColor"
app:srcCompat="@drawable/ic_person_black_24dp" />
</TableRow>
</TableLayout>
</code></pre>
| 0non-cybersec
| Stackexchange |
Number of onto mappings from set {1,2,3,4,5} to the set {a,b,c}. <p>This is based on the question <a href="https://answers.yahoo.com/question/index?qid=20081203110933AAiSaM1" rel="nofollow">at here</a></p>
<p>I want to know how many onto functions are there from set $A={1,2,3,4,5}$ to set $B={a,b,c}$. </p>
<p>This is how I did it:
First i tried to find the functions which are not onto<br>
<em>case 1:</em>
All in A maps to a single element of B<br>
There are 3 ways for this </p>
<p><em>case2:</em><br>
When mappings are made for only two elements in range.<br>
First we have to select 2 out of 3 elements.That can be done in $3\choose 2$$=3$ways.<br>
Consider mappings to only (a,b).<br>
Number of ways when only one item maps to a=5<br>
Number of ways when only two items maps to a=$5\choose 2$<br>
Number of ways when only three items maps to a=$5\choose 3$ </p>
<p>Number of ways when only four items maps to a=$5\choose 4$<br>
Total mappings only to (a,b)=30.<br>
Hence in case 2 total non onto mappings are$=30*3=90$ </p>
<p>By case1 and case2 Total non onto mappings are $90+3=93$ </p>
<p>Therefore onto mappings are $3^5=93=150$ </p>
<p>My question is in the given answer mappings for <strong>case2</strong> is obtained as <code>, there are 2^5 = 32 possible functions, so we have 3*32 = 96 functions here that aren't onto</code>. </p>
<p>What's wrong with my method?<br>
Can someone please tell me where I have done wrong?</p>
| 0non-cybersec
| Stackexchange |
Is there an API for Apple App Analytics?. <p>I'm trying to extract the analytics information of my App in the Apple App Store using an API.</p>
<p>I have been able to just download the information but I need a more automate solution. </p>
<p><a href="https://developer.apple.com/app-store/app-analytics/" rel="nofollow noreferrer">https://developer.apple.com/app-store/app-analytics/</a>
<a href="https://itunespartner.apple.com/en/apps/faq/App%20Analytics_Overview" rel="nofollow noreferrer">https://itunespartner.apple.com/en/apps/faq/App%20Analytics_Overview</a></p>
<p>And I cannot find any information in the documentation. Any Idea ?</p>
| 0non-cybersec
| Stackexchange |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
where is com.google.android.gcm.GCMBaseIntentService?. <p>I'm following the tutorial on GCM here <a href="http://developer.android.com/guide/google/gcm/gs.html">http://developer.android.com/guide/google/gcm/gs.html</a></p>
<p>At point 5 of <strong>Step 2</strong>, it says: </p>
<blockquote>
<p>Add the following intent service:
service android:name=".GCMIntentService"</p>
</blockquote>
<p>This intent service will be called by the GCMBroadcastReceiver (which is is provided by GCM library), as shown in the next step. It must be a subclass of <code>com.google.android.gcm.GCMBaseIntentService</code>, must contain a public constructor, and should be named <code>my_app_package.GCMIntentService</code> (unless you use a subclass of <code>GCMBroadcastReceiver</code> that overrides the method used to name the service).</p>
<p>However, I can't subclass <code>com.google.android.gcm.GCMBaseIntentService</code>, the import can't be resolved. How do I fix this?</p>
| 0non-cybersec
| Stackexchange |
Why would an HTTP(S) request not be logged in IIS?. <p>I'm troubleshooting a batch file that uses <a href="http://www.gnu.org/software/wget/" rel="nofollow noreferrer">Wget</a> to send requests to a website running in IIS 7. The batch file runs Wget twice, the first time to login to the site via a POST, the second to run some maintenance code in the site via a GET. The server running the batch file and the server hosting the site are on the same private network.</p>
<p>The first POST request is logged in the IIS site log. According to the output of Wget, it appears to be making several attempts for the second GET request – 20 in total (usually) – but none of them are being logged.</p>
<p>The (edited) contents of the problematic batch file:</p>
<pre><code>wget --output-document=- --save-cookies cookies.txt --keep-session-cookies --post-data "[email protected]&Password=not-the-best-password&RememberMe=false" --no-check-certificate https://example.com/account/logon?returnurl=/
wget --output-document=- --load-cookies cookies.txt --no-check-certificate https://example.com/things/stuff/maintenance-code?x=E74B15D4-414E-468C-A340-621CC901CF1B
</code></pre>
<p>An (edited) example of the Wget (standard error) output for the first two attempts for the second GET request from the latest execution of the batch file:</p>
<pre><code>SYSTEM_WGETRC = c:/progra~1/wget/etc/wgetrc
syswgetrc = C:\Program Files (x86)\GnuWin32/etc/wgetrc
--2013-04-19 05:15:16-- https://example.com/things/stuff/maintenance-code?x=E74B15D4-414E-468C-A340-621CC901CF1B
Resolving example.com... 172.17.21.255
Connecting to example.com|172.17.21.255|:443... connected.
WARNING: cannot verify example.com's certificate, issued by `blah-blah-blah':
Self-signed certificate encountered.
HTTP request sent, awaiting response... Read error (No such file or directory) in headers.
Retrying.
--2013-04-19 05:20:21-- (try: 2) https://example.com/things/stuff/maintenance-code?x=E74B15D4-414E-468C-A340-621CC901CF1B
Connecting to example.com|172.17.21.255|:443... connected.
WARNING: cannot verify example.com's certificate, issued by `blah-blah-blah':
Self-signed certificate encountered.
HTTP request sent, awaiting response... Read error (No such file or directory) in headers.
Retrying.
</code></pre>
<p>There is another batch file that also uses Wget and also runs it twice, the first time to login exactly as the other batch file does, and the second time to run some <em>other</em> maintenance code in the site and also via a GET, and both the POST and GET requests are logged in IIS. An edited example of the Wget (standard error) output for the GET request for the latest execution of this batch file:</p>
<pre><code>SYSTEM_WGETRC = c:/progra~1/wget/etc/wgetrc
syswgetrc = C:\Program Files (x86)\GnuWin32/etc/wgetrc
--2013-04-19 06:58:50-- https://example.com/things/other-stuff/other-maintenance-code
Resolving example.com... 172.17.21.255
Connecting to example.com|172.17.21.255|:443... connected.
WARNING: cannot verify example.com's certificate, issued by `blah-blah-blah':
Self-signed certificate encountered.
HTTP request sent, awaiting response... 200 OK
Length: 15 [application/json]
Saving to: `STDOUT'
0K 100% 2.05M=0s
2013-04-19 06:59:06 (2.05 MB/s) - `-' saved [15/15]
</code></pre>
| 0non-cybersec
| Stackexchange |
Do You Have Time? How About Wasting It?. | 0non-cybersec
| Reddit |
Incompatibility between fontspec and graphicx (bug of XeTeX). <p>I got a weird problem with the <a href="http://ctan.org/pkg/fontspec" rel="nofollow noreferrer"><code>fontspec</code></a> package and the <a href="http://ctan.org/pkg/graphicx" rel="nofollow noreferrer"><code>graphicx</code></a> package. Let's see the MWE first.</p>
<pre><code>%!TEX program = xelatex
\documentclass{article}
\usepackage{graphicx}
\usepackage{fontspec}
\setmainfont{Times New Roman}
\newfontfamily\test[AutoFakeBold = 5]{Times New Roman}
\begin{document}
\test
Test
\textbf{Bold Test}
\includegraphics[scale = 0.1]{photo}
Words that shouldn't be bolded. Even if \textmd{textmd-ed}.
\end{document}
</code></pre>
<blockquote>
<p><img src="https://ww3.sinaimg.cn/large/005yyi5Jjw1enwheh2gb8j30um0ietbx.jpg" alt=""></p>
</blockquote>
<p>In the preamble, I loaded the <code>graphicx</code> package and the <code>fontspec</code> package, then I set <code>Times New Roman</code> as the default font of the text as well as the font of the <code>test</code> command. In the definition of <code>\test</code>, I enabled <code>AutoFakeBold</code>. In the document body, between the two chains of text, I inserted a photo with the <code>\includegraphics</code> command.</p>
<p>It's a normal manuscript, except that <code>AutoFakeBold</code> was set to <code>5</code> to make the abnormal output more remarkable. After the compilation, however, the later line of text presented an unexpected output. That is, this line of text shouldn't be bolded.</p>
<p>Even more surprising is that, if one</p>
<ul>
<li>cancel the option passed to <code>\includegraphics</code>,</li>
<li>or put some more text after <code>\textbf{}</code>,</li>
</ul>
<p>the problem will go away.</p>
<p>I suspect the problem lies in the <code>FakeBold</code> mechanism of the <code>fontspec</code> package and/or the key-val mechanism of the <code>graphicx</code> package, but unfortunately, I don't read LaTeX3 codes, so I cannot locate it.</p>
<p>Maybe an issue should be posted to <code>fontspec</code> or <code>graphicx</code>, but before that, could someone provide me a quick fix to this problem?</p>
<hr>
<p><strong>EDIT 2015/01/05</strong></p>
<p>Thanks to the help of [email protected], it seems to be a bug of XeTeX. See the new MWE.</p>
<pre><code>% !TeX program = xetex
\font\x="[cmunrm.otf]"
\font\bx="[cmunrm.otf]:embolden=5;"
\x Test
{\bx Bold Test}
\XeTeXpicfile "example-image.png" width 1cm\relax
Words that shouldn't be bolded.
\tracingoutput=1
\showboxbreadth=\maxdimen
\showboxdepth=\maxdimen
\bye
</code></pre>
<blockquote>
<p><img src="https://ww1.sinaimg.cn/large/005yyi5Jjw1enz43u9nnej31cq07kab7.jpg" alt=""></p>
</blockquote>
<p>I made a ticket on <a href="https://sourceforge.net/p/xetex/bugs/105/" rel="nofollow noreferrer">xetex.sf</a> and hope this will be fixed soon.</p>
| 0non-cybersec
| Stackexchange |
2020 Chevy Camaro SS gets emergency facelift. | 0non-cybersec
| Reddit |
Is it good practice to use Angular Flex-Layout?. <p>I would like to know if it really is a good practice to use Angular Flex-Layout module. Isn't it just sugar coated inline styles with extra performance cost since it's JavaScript that does the styling?
So if you can, please explain to me why I should use it over basic flex box?</p>
| 0non-cybersec
| Stackexchange |
Rimmel Volume Accelerator Mascara, Black Reviews. | 0non-cybersec
| Reddit |
Show the "clock"and Euclidean metrics generate different topologies. <p>I'm trying to teach my self topology. I wanted to find an example of a metric generating different topology. I came up with what a call "clock" metric, inspired by the modulo operation. <br> Can anyone please look this over and verify that my reasoning is correct. Also, does this type of metric have a standard name, and/or generalization to higher dimensions?</p>
<p><br>.............................................................<br>
Clock metric:
$$d(x,y)=6-||x-y|-6|$$
The distance between two numbers on a clock. Ex $d(2,11)=3$ (see diagram)
<br>
<a href="https://i.stack.imgur.com/6g4WV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6g4WV.png" alt="enter image description here"></a></p>
<blockquote>
<p>Show the clock metric(above) and the Euclidean metric generate different topologies on the set [1,13).</p>
</blockquote>
<p>Consider the open ball $B_{2}^{clock}(1)=(11,13) \cup [1,3)$. There does not exist $0<r<2$, such that $\{12\}\in B_{r}^{Eucl}(1)$.Since $r$ does not exist, the topologies generated must be different. </p>
| 0non-cybersec
| Stackexchange |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
GHC's RTS options for garbage collection. <p>I have a Haskell program which processes a text file and builds a <code>Map</code> (with several million elements). The whole thing can run for 2-3 minutes. I found that tweaking the -H and -A options makes a big difference in running time.</p>
<p>There is <a href="https://downloads.haskell.org/~ghc/8.4.2-rc1/docs/html/users_guide/runtime_control.html#rts-options-to-control-the-garbage-collector" rel="nofollow noreferrer">documentation</a> about this functionality of the RTS, but it's a hard read for me since I don't know the algorithms and terms from GC theory. I'm looking for a less technical explanation, preferably specific to Haskell/GHC. Are there any references about choosing sensible values for these options?</p>
<p>EDIT:
That's the code, it builds a trie for a given list of words.</p>
<pre><code>buildTrie :: [B.ByteString] -> MyDFA
buildTrie l = fst3 $ foldl' step (emptyDFA, B.empty, 1) $ sort $ map B.reverse l where
step :: (MyDFA , B.ByteString, Int) -> B.ByteString -> (MyDFA , B.ByteString, Int)
step (dfa, lastWord, newIndex) newWord = (insertNewStates, newWord, newIndex + B.length newSuffix) where
(pref, lastSuffix, newSuffix) = splitPrefix lastWord newWord
branchPoint = transStar dfa pref
--new state labels for the newSuffix path
newStates = [newIndex .. newIndex + B.length newSuffix - 1]
--insert newStates
insertNewStates = (foldl' (flip insertTransition) dfa $ zip3 (branchPoint:init newStates) (B.unpack newSuffix) newStates)
</code></pre>
| 0non-cybersec
| Stackexchange |
I was wondering how everyone goes about using their leftover ingredients and how they can be reused (e.g. stale bread = croutons for soup!). In eating cheap and healthy, what we do with leftovers and food that’s about to go out of date is important.
I get a lot of off days, so frequently end up with a bunch of food that I need to use up before it goes out of date. I recently figured out that stale bread can be cut up and dried in an oven to make croutons (mash them up and you’ll get breadcrumbs) and have been looking into pickling foods (like cucumber, jalapeños, etc.).
I’m aware that many things can be frozen,but does anyone have other ways of using up their spare food?
Edit: I also like using past-their-best veg for soups and stock that I throw into the freezer. | 0non-cybersec
| Reddit |
How to use a windows 8 laptop at Starbucks . | 0non-cybersec
| Reddit |
Complete Carelessness. 🤦. | 0non-cybersec
| Reddit |
slow vnc connection to a vmware workstation virtual machine. <p>I've got 2 computers :
-host in which is installed workstation 12 and a VM called "guest" (linux)
- a laptop, in the same room as the host</p>
<p>I get a fine wired connection between the 2 computers (host+a laptop), but, using wifi + VNC, the graphical user interface of the guest OS has a lag, the moves of the mouse cursor are slow, the windows take a long time to be moved too</p>
<p>here is some technical stuff:
- host : a barebone with 16Gb of memory, the OS is linux mint 17.3
- guest : fedora x64
- laptop : lenovo + core i3, OS : windows 10 x64. VNC client : realVNC
- the wifi connection between host & laptop is in theory of 430 Mb, but the measures give 65 Mb(it passes through the box which slows the connection)</p>
<p>I have 2 questions:
-is it possible to have a decent control over the guest through the laptop via wifi?
-if so, what is the minimum required speed?
-if the connection is too slow, what are the particular points which slow the connection?(the VNC server in host?the speed of the wifi connection?the host hard disk accesses?..)</p>
<p>thanks.
olivier </p>
| 0non-cybersec
| Stackexchange |
verify sshd configuration. <p>How I can verify the configuration of <code>sshd</code>?</p>
<p>For example, I want to make sure that these settings are set and applied:</p>
<pre><code>AllowUsers user1 user2
PasswordAuthentication no
PermitRootLogin no
</code></pre>
<p>Is the only way manually verifying the contents of the file <code>sshd_config</code>, or can I probe <code>sshd</code> to make sure?</p>
| 0non-cybersec
| Stackexchange |
Probability question using PIE. <p>Five people check identical suitcases before boarding an airplane. At the baggage claim, each person takes one of the five suitcases at random. What is the probability that every person ends up with the wrong suitcase?</p>
<p>I think I need to use the principle of inclusion exclusion to solve this but I'm not quite sure how.</p>
| 0non-cybersec
| Stackexchange |
Problem booting node with PXE Ubuntu MAAS. <p>I'm having problem with adding nodes in Ubuntu MAAS, it boots when I'm adding it in web interface but when the node boots it doesn't boot any PXE files or find the master computer.</p>
<pre><code>PXE-E76: Bad or missing multicast discovery address
PXE-M0F: Exiting HP PXE ROOM
</code></pre>
<p><img src="https://i.stack.imgur.com/BfH0U.jpg" alt="enter image description here"></p>
| 0non-cybersec
| Stackexchange |
Controlling `\subsection` output at `.toc` file. <p>Consider the following simple code</p>
<pre><code>\documentclass[12pt]{article}
\usepackage [english] {babel}
\begin{document}
\tableofcontents
\section{One}
\subsection{Two}
\subsection{Three}
\end{document}
</code></pre>
<p>It will produce the <code>.toc</code> file with the following inside</p>
<pre><code>\select@language {english}
\contentsline {section}{\numberline {1}One}{1}
\contentsline {subsection}{\numberline {1.1}Two}{1}
\contentsline {subsection}{\numberline {1.2}Three}{1}
</code></pre>
<p>Then if I will format my table of contents with <code>tocloft</code> package I will always have a deal with numbers of sections formatted as <code><section>.<subsection></code>. My question is if it is possible to control output of <code>\subsection</code> command into <code>.toc</code> file to obtain in <code>.toc</code> file numbers of subsections formatted as <code><subsection></code>:</p>
<pre><code>\select@language {english}
\contentsline {section}{\numberline {1}One}{1}
\contentsline {subsection}{\numberline {1.1}Two}{1}
\contentsline {subsection}{\numberline {1.2}Three}{1}
</code></pre>
<p>(P.S. I use <code>titlesec</code> and <code>titleloft</code> packages and then if there are no proper easy solution I would like to have a solution that doesn't affect work of these packages).</p>
| 0non-cybersec
| Stackexchange |
His first time to the vet. | 0non-cybersec
| Reddit |
Windows Server 2012 R2 Conditional Expressions NTFS Security. I have a Windows Server 2012 R2 file server. I shared a top-level folder called "Shares." In that shares folder, I have sub-folders for our branch offices. Let's say one is called Arizona. The idea is to grant access to these folders only if you are on a computer in the branch office.
I've added the Arizona computers to a security group. I gave domain users modify permissions to the Arizona folder, and added a condition. The condition settings are Device, Group, Member of any, value, "Arizona computers" security group.
I expected this setup to have this behavior. John Doe is a member of domain users obviously. John Doe logs onto a PC in Pittsburgh, and cannot access the folder because of the added condition. John Doe logs onto a computer in Arizona (that is in the security group), and is able to access the folder. Is this correct? Because I am not able to access the folder.
Thanks. | 0non-cybersec
| Reddit |
Oh. You're home early.. | 0non-cybersec
| Reddit |
Create Powerpoint with JavaScript. <p>JavaScript cannot create files locally on the clients filesystem. However, I am wondering, if it is possible to somehow create a Powerpoint MIME in a web page (a div or a iframe) from some JSON and then let the UserAgent figure out it is Powerpoint in the expectation that the UserAgent will offer the user the choice to display it as a powerpoint presentation? </p>
<p>Note: The idea here is to be able to take some JSON and make a powerpoint presentation without having to make a request to a Server to create a Powerpoint file.</p>
| 0non-cybersec
| Stackexchange |
Why is the closed-form evaluation of the Catmull-Rom spline numerically unstable?. <p>According to the <a href="https://en.wikipedia.org/wiki/Cubic_Hermite_spline" rel="nofollow noreferrer">related Wikipedia article</a>, a cubic Hermite spline, on the unit interval <span class="math-container">$[0, 1]$</span>, is defined as</p>
<p><span class="math-container">$$
\mathbf{p}(t) = (2t^3-3t^2+1)\mathbf{p}_0 + (t^3-2t^2+t)\mathbf{m}_0 + (-2t^3+3t^2)\mathbf{p}_1 +(t^3-t^2)\mathbf{m}_1 \tag{1}\label{1}
$$</span></p>
<p>where <span class="math-container">$\mathbf{p}_0$</span> and <span class="math-container">$\mathbf{p}_1$</span> are two successive control points (the points to interpolate) and <span class="math-container">$\mathbf{m}_0$</span> and <span class="math-container">$\mathbf{m}_1$</span> are the tangents at those points.</p>
<p>The Catmull-Rom spline is also a cubic Hermite spline. However, in the <a href="https://en.wikipedia.org/wiki/Centripetal_Catmull%E2%80%93Rom_spline" rel="nofollow noreferrer">associated Wikipedia article</a>, the evaluation or computation of the spline is performed using a numerical algorithm based on or similar to the <a href="https://en.wikipedia.org/wiki/De_Boor%27s_algorithm" rel="nofollow noreferrer">De Boor's algorithm</a>. How is the numerical algorithm (in the Catmull-Rom Wikipedia article) exactly related to the \eqref{1}? Why do we need this numerical algorithm, or, in other words, why is it unstable to just evaluate \eqref{1} at some <span class="math-container">$t \in [0, 1]$</span>?</p>
| 0non-cybersec
| Stackexchange |
Shiny Delphox fan art I made. | 0non-cybersec
| Reddit |
Send form daily/automatically. <p>I was wondering if anyone knows a way of sending a Google Form daily and automatically to someone? </p>
<p>More specifically, I am a tutor who would like to send a HW check-in to my students daily, but I would love for it to just be sent automatically every day rather than having to do it manually.</p>
| 0non-cybersec
| Stackexchange |
Cups printer “sleeping” for the first 10-30 minutes after computer power on. <p>I have an HP Deskjet 1510 connected via usb to an Ubuntu Server 12.04 LTS. I have turned off the "Automatically power off printer after 2 hours to save energy" feature by connecting the printer to a Windows machine and disabling it through HP's software. So the printer is powered on 24/7 (led lit and all that) even when the server is shut down.</p>
<p>The printer is being shared to my local network through cups. The sharing works, I can actually print from various Windows devices in my network with no problem.</p>
<p>The issue is, when I power on the server (the actual machine I mean), If I start sending files for printing to the HP Deskjet they just get filled in the windows queue. I mean the one where it says</p>
<p><code>x document(s) pending for User</code></p>
<p>If I got to</p>
<p><code>https://192.168.2.15:631/printers/HP_Deskjet_1510</code> (<code>192.168.2.15</code> being the local ip of my server)</p>
<p>This is the screen that I get</p>
<p><a href="https://i.stack.imgur.com/gSXAm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gSXAm.png" alt="screen shot"></a></p>
<p>No jobs queued.</p>
<p>I've tried the following commands in the server after searching on the internet. After each command I sent a page for printing from microsoft word to see if it would work. It didn't</p>
<pre><code># hp-probe
HP Linux Imaging and Printing System (ver. 3.15.7)
Printer Discovery Utility ver. 4.1
Copyright (c) 2001-15 Hewlett-Packard Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.
--------------------------------
| SELECT CONNECTION (I/O) TYPE |
--------------------------------
Num Connection Description
Type
-------- ---------- ----------------------------------------------------------
0* usb Universal Serial Bus (USB)
1 net Network/Ethernet/Wireless (direct connection or JetDirect)
Enter number 0...1 for connection type (q=quit, enter=usb*) ? 0
Using connection type: usb
--------------------
| DEVICE DISCOVERY |
--------------------
warning: No devices found on the 'usb' bus. If this isn't the result you are expecting,
warning: check to make sure your devices are properly connected and powered on.
Done.
# sudo /usr/lib/cups/backend/usb
DEBUG: list_devices
DEBUG: libusb_get_device_list=7
DEBUG2: Printer found with device ID: MFG:HP;MDL:Deskjet 1510 series;CMD:PCL3GUI,PJL,Automatic,DW-PCL,DESKJET,DYN;CLS:PRINTER;DES:B2L57C;CID:HPDeskjet_P976D;LEDMDIS:USB#FF#CC#00,USB#07#01#02,USB#FF#04#01;SN:CN5192F06B05XJ;S:038000C484a01021002c1f00046c288005a;J: ;Z:0102,0503872800b048,0600,0c0,0e00000000,0f00000000,10000008000008,12000,147,150,16361a3872000316da186a0003,17000000000000,180; Device URI: usb://HP/Deskjet%201510%20series?serial=CN5192F06B05XJ&interface=1
direct usb://HP/Deskjet%201510%20series?serial=CN5192F06B05XJ&interface=1 "HP Deskjet 1510 series" "HP Deskjet 1510 series" "MFG:HP;MDL:Deskjet 1510 series;CMD:PCL3GUI,PJL,Automatic,DW-PCL,DESKJET,DYN;CLS:PRINTER;DES:B2L57C;CID:HPDeskjet_P976D;LEDMDIS:USB#FF#CC#00,USB#07#01#02,USB#FF#04#01;SN:CN5192F06B05XJ;S:038000C484a01021002c1f00046c288005a;J: ;Z:0102,0503872800b048,0600,0c0,0e00000000,0f00000000,10000008000008,12000,147,150,16361a3872000316da186a0003,17000000000000,180;" ""
# sudo usb_printerid /dev/usb/lp0
GET_DEVICE_ID string:
MFG:HP;MDL:Deskjet 1510 series;CMD:PCL3GUI,PJL,Automatic,DW-PCL,DESKJET,DYN;CLS:PRINTER;DES:B2L57C;CID:HPDeskjet_P976D;LEDMDIS:USB#FF#CC#00,USB#07#01#02,USB#FF#04#01;SN:CN5192F06B05XJ;S:038000C484a01021002c1f00046c288005a;J: ;Z:0102,0503872800b048,0600,0c0,0e00000000,0f00000000,10000008000008,12000,147,150,16361a3872000316da186a0003,17000000000000,180;
# lpstat -t
scheduler is running
no system default destination
device for HP_Deskjet_1510: usb://HP/Deskjet%201510%20series?serial=CN5192F06B05XJ&interface=1
HP_Deskjet_1510 accepting requests since Fri 27 Nov 2015 03:54:47 PM EET
printer HP_Deskjet_1510 is idle. enabled since Fri 27 Nov 2015 03:54:47 PM EET
# lpstat -v
device for HP_Deskjet_1510: usb://HP/Deskjet%201510%20series?serial=CN5192F06B05XJ&interface=1
# sudo cupsenable HP_Deskjet_1510
# lpc status
HP_Deskjet_1510:
printer is on device 'usb' speed -1
queuing is enabled
printing is enabled
no entries
daemon present
# sudo service cups restart
cups stop/waiting
cups start/running, process 2706
</code></pre>
<p>The printer remains in this derp mode for like 10-30 mins as I said. After that time, if I start printing, It prints normally. I kind of feels like that the print job is not being sent to the server? The driver that I'm using in windows is Public Image Setter (it was the only one that worked).</p>
| 0non-cybersec
| Stackexchange |
Why is System reading thousands of images from my hard drive constantly?. <p>I have been getting poor performance while playing Minecraft recently, and I open up Resource monitor to see this:</p>
<p><img src="https://i.stack.imgur.com/p0vCj.png" alt="Crazy disk usage!"></p>
<p>Actually when I first opened it, I saw that pagefile.sys was at the top of the list, and I have 8 gigs of ram, 4 gigs of which is free when the computer is "idle", i.e. when I'm not playing my game. I'm wondering if that is caused by whatever System is doing with my pictures.</p>
<p>I've started considering disabling my page file, since MS says if a system has enough ram the pagefile most likely won't be necessary, but if this other thing keeps happening that's going to be a problem.</p>
<p>It just occurred to me that my C drive is 90% full at this point, could this be causing all of this?</p>
| 0non-cybersec
| Stackexchange |
How to group by the first element of an array?. <p>I work with documents such as:</p>
<pre><code>{
"foo" : { "objectid" : "39", "stuff" : "65" },
"yearpublished" : ["1979"],
"bar" : "1263"
}
</code></pre>
<p><code>yearpublished</code> is an array and I would like to group my collection by the first value in this array and then count the amount of documents related.</p>
<p>I have written this query:</p>
<pre><code>db.foobar.aggregate([
{ $group : {
_id : '$yearpublished',
count: { $sum: 1 }
}}
])
</code></pre>
<p>and get:</p>
<pre><code>{
"result" : [
{ "_id" : ["1923"], "count" : 1.0000000000000000 },
{ "_id" : ["1864"], "count" : 1.0000000000000000 }
]
}
</code></pre>
<p>But I'm looking for this kind of result (i. e. first element only):</p>
<pre><code>{
"result" : [
{ "_id" : "1923", "count" : 1.0000000000000000 },
{ "_id" : "1864", "count" : 1.0000000000000000 }
]
}
</code></pre>
<p>I've also tried <code>_id : { $first: '$yearpublished.0' },</code> or <code>_id : { $first: '$yearpublished[0]' },</code> without success.</p>
<p>How can I group by the first element of the array <strong>yearpublished</strong> ?</p>
| 0non-cybersec
| Stackexchange |
Don't get pinched. | 0non-cybersec
| Reddit |
Server RAID0: one hdd is more %busy then the others?. <p>I'm testing 3 servers with RAID0 with 4 disks. During my test I noticed on all 3 servers that one of the hdd's is more %busy and has much higher averige IO wait (almost 4x higher then the other hdd's). It's always the "last" disk on the server. The disks in the servers are all the same model (number) so they should have the same results in RAID0 as far as I understand? (*to be honest I'm not sure if the servers are software raid or hardware raid)</p>
<p>I would like to know if that is normal in a RAID0 system? Why does does one disk have a higher IO wait? I did find a clue, see my last image where it shows the "Request size", it's 2x to 3x smaller then the other disk(s) what does that say? Maybe some setting I can change for the disk? *graphics are created by Munin.</p>
<p><img src="https://i.stack.imgur.com/FTyAe.png" alt="graphics io usage"></p>
<p><img src="https://i.stack.imgur.com/rgUNc.png" alt="graphics io usage2"></p>
<p>Extra information after requested:</p>
<pre><code>cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid0 sda5[0] sdc1[2] sdd1[3] sdb1[1]
11713146880 blocks super 1.2 512k chunks
unused devices: none
mount
/dev/md0 on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/cgroup type tmpfs (rw)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755)
none on /sys/fs/pstore type pstore (rw)
/dev/sda4 on /tmp type ext4 (rw,noexec,nosuid,nodev)
/dev/sda2 on /boot type ext2 (rw)
systemd on /sys/fs/cgroup/systemd type cgroup (rw,noexec,nosuid,nodev,none,name=systemd)
cat /proc/swaps
Filename Type Size Used Priority
/dev/sda3 partition 3906556 60 -1
</code></pre>
| 0non-cybersec
| Stackexchange |
funny science for real. | 0non-cybersec
| Reddit |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
Host DNS server. <p>I just switched to dedicated hosting for my web server and my host does not provide DNS services. Is it good practice to host a DNS server on the same machine as my web server?</p>
| 0non-cybersec
| Stackexchange |
This little guy was in my bong while i hit it; he spent the next half hour chilling on my lampshade. | 0non-cybersec
| Reddit |
Full List of New Horror Movies Being Released in April 2017 (add on if you see that something is missing). | 0non-cybersec
| Reddit |
Good Hip Hop Movies, Books, Documentaries?. After watching Straight Outta Compton, I was wondering if there were any other movies or documentaries related to and about hip hop and the history of rap? Also any books about rap would be cool. Like the Rap Yearbook written by the woman who did an AMA a couple weeks ago. That was a very interesting and entertaining read. If any one has any suggestions that would be great.
Thanks. | 0non-cybersec
| Reddit |
how to access usb drive in raspbian terminal?. Hi folks.
I have installed Raspbian Buster Lite on a headless pi zero w. I've SSH into the Pi0W into a terminal. The problem is that I log in as a normal user, not the root.
I have plugged in a usb drive. When I type in 'sudo fdisk -l', it shows the usb device as '/dev/sda1'.
So I type
sudo mkdir /media/usb-drive
sudo mount /dev/sda1 /media/usb-drive/
Then I try to access the drive:
cd /media/usb-drive
But get the error message: 'cd: /media/usb-drive/: Permission denied' because I am not root.
So I try 'sudo cd /media/usb-drive' and get the error message 'cd: command not found.
So how do I access the usb drive as a normal user? And if the only way for me to access the drive is as root, how can I become root? According to the raspberry documentation, users can only use 'sudo' to execute some commands as root, but I can't find any information via google about how to actually become root.
[https://www.raspberrypi.org/documentation/linux/usage/root.md](https://www.raspberrypi.org/documentation/linux/usage/root.md)
Any and all help would be greatly appreciated. :) | 0non-cybersec
| Reddit |
Adding subtotals to SSRS report tablix. <p>say i have this record..</p>
<pre>
lastname firstname mi checkno amount totalamount
lastname1 firstname1 mi1 k1234 5000
lastname2 firstname2 mi2 k1234 5000
lastname3 firstname3 mi3 k1234 5000
lastname4 firstname4 mi4 k90788 5000
lastname5 firstname5 mi5 k90788 5000
lastname6 firstname6 mi6 k90789 5000
30000
</pre>
<p>can i make this record to look like the following in ssrs?</p>
<pre>
lastname firstname mi checkno amount totalamount
lastname1 firstname1 mi1 k1234 5000
lastname2 firstname2 mi2 k1234 5000
lastname3 firstname3 mi3 k1234 5000
15000
lastname4 firstname4 mi4 k90788 5000
lastname5 firstname5 mi5 k90788 5000
10000
lastname6 firstname6 mi6 k90789 5000
5000
</pre>
<p>hope anyone can help me fix this. thank you</p>
| 0non-cybersec
| Stackexchange |
How to use just Nickname instead of Full name on G+?. <p>I'm following these Desktop <a href="https://support.google.com/plus/answer/3298988" rel="nofollow">steps</a> to add the nickname for my G+ profile, however I'm not able to use my nickname to display on comments.</p>
<p>For example going to some <a href="https://chrome.google.com/webstore/detail/easy-check/ldopaogbegnhconlboidfjcmidndkbeg/reviews" rel="nofollow">Chrome web store</a> and posting the comment using my Google account, I would like to see my nickname instead of full name.</p>
<p>Is it possible?</p>
| 0non-cybersec
| Stackexchange |
Xfce, applet indicator-cpufreq, not working when set to Powersafe from Performance. <p><strong>Os</strong></p>
<pre><code>Linux local 5.0.0-23-lowlatency #24-Ubuntu SMP PREEMPT Mon Jul 29 16:17:02 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
xfce4-panel 4.13.4 (Xfce 4.12)
</code></pre>
<p><strong>Issue</strong></p>
<p>I am using <code>indicator-cpufreq</code> applet. Everything is ok, switching from <code>Powersafe</code> to <code>Performance</code> and back is ok, but sometimes switch from <code>Performance</code> to <code>Powersafe</code> don't work, when I am using <code>Performance</code> for a long time. I checked it via <code>lscpu</code>.</p>
<pre><code>CPU MHz: 3500.181
CPU max MHz: 3500,0000
CPU min MHz: 400,0000
</code></pre>
<p>Only restart helped.</p>
<p>Where is the catch? How can I switch to <code>Powersafe</code> mode from terminal?</p>
<p>Thanks.</p>
| 0non-cybersec
| Stackexchange |
PhpMyAdmin 4.9.0.1 export MySQL Database latin1_swedish_ci and reimport as UTF-8. <p>I have to update a quite old CMS-system to a new one on an other webspace. This means also a new database.</p>
<p>The original database can't be modified, because at the moment the CMS is in use. There is also no direct access to the database, for example with mysqldump.</p>
<p>The only thing i have, is PhpMyAdmin 4.9.0.1 and i need to export the database and reimport it into the new database with charset UTF-8.</p>
<p>The original database tells me: MyISAM latin1_swedish_ci</p>
<p>With the new database i also have only PhpMyAdmin.</p>
<p>How can i transform the data to UTF-8?</p>
<p>Thank you.</p>
| 0non-cybersec
| Stackexchange |
🔥 Giant Oceanic Manta Ray spotted under offshore rig near Trinidad (shark for scale)🔥. | 0non-cybersec
| Reddit |
Visio 2013 won't allow master shape edit even with protection turned off. <p>I've made a new stencil, I've dropped in a shape to edit, I'm editing it. It's a swimlane, and I want to rotate the title block. I've turned on developer mode, and put protection to "none".</p>
<p>I can see the rotation handle but I can't drag it. I can select rotate 90 degrees right, but it just doesn't happen.</p>
<p>I've had a look at the layers, but there doesn't seem to be a check box next to "lock" as I've seen described.</p>
<p>I just want to change the shape and it's not letting me.</p>
| 0non-cybersec
| Stackexchange |
On a characterization of the Gårding subspace of the left regular representation of reals. <p>Consider the left regular representation of $\mathbb{R}$ in $\mathrm{L}^2(\mathbb{R})$. Let us denote by $\mathrm{L}^2(\mathbb{R})^\infty$ the algebraic subspace of smooth vectors, or equivalently, the Gårding subspace (the theorem of Dixmier-Malliavin assumed to be at our disposal). I want to prove</p>
<p>$$\mathrm{L}^2(\mathbb{R})^\infty =
\{f\in\mathcal{C}^\infty(\mathbb{R}) \mid
f^{(n)}\in\mathrm{L}^2(\mathbb{R})\:\:\text{for all}\:\:n\geq 0\}.$$</p>
<p>Actually, I proved the inclusion $\subseteq$ by making use of an exercise in Knapp's <em>Representation Theory of Semisimple Groups</em> (Problem 5 on p. 57). My questions are: Is the above equality really true? If so, could you please give a reference, or an argument for the proof of $\supseteq$?</p>
| 0non-cybersec
| Stackexchange |
Can the Cesaro limit of a positive definite function be negative?. <p>Let $G$ be a countable amenable group and $\gamma:G\to\mathbb{C}$ a positive (semi)definite function (i.e. such that $\gamma(g^{-1})=\overline{\gamma(g)}$ and
$$\sum_{g,h\in G}f(g)\overline{f(h)}\gamma(h^{-1}g)\geq0$$
whenever $f:G\to\mathbb{C}$ is finitely supported).
Let $(F_N)_{N\in\mathbb{N}}$ be a Folner sequence in $G$ and assume the Cesaro limit
$$L:=\lim_{N\to\infty}\frac1{|F_N|}\sum_{g\in F_N}\gamma(g)$$
exists. Can $L$ be negative?</p>
<p>If $G$ is abelian then one can apply Bochner-Herglotz theorem to represent $\gamma$ as the Fourier transform of a positive measure, decompose it into atomic and continuous components, and then apply Wiener's lemma to the continuous component.
It follows that $L\geq0$.
Can this proof be adapted to the amenable case?</p>
| 0non-cybersec
| Stackexchange |
memory usage doesn't add up. <blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="https://askubuntu.com/questions/41040/how-do-i-get-the-actual-used-memory-including-ram-disks">How do I get the actual used memory including RAM disks?</a> </p>
</blockquote>
<p>If I add up all the memory usage I get from top -b -n 1 or htop or ps aux, I get a number that is a few GB under what I get with free. The kernel could account for some of that memory, but not up to a few GB, could it ?</p>
| 0non-cybersec
| Stackexchange |
Windows-To-Go - Block access to data when connected to a normal Windows PC. <p>We would like to use Windows-To-Go in our company.<br/>
I have installed it on a Windows-To-Go certified USB key.</p>
<p>I really love it, but I'm a little concerned regarding access to the file-system.
<br/>
<br/></p>
<h2>The setup</h2>
<ul>
<li>Windows 8.1 Enterprise</li>
<li>Local user account. No admin permissions</li>
<li>Bitlocker encrypted with a PIN (PIN is the only option when using Windows-To-Go)
<br/>
<br/></li>
</ul>
<h2>The situation</h2>
<p>We would like to give this key to users so they can work from home. (They use it to start a VPN session and connect to a VMware VDI Windows session)<br/>
To boot they need to fill in the encryption PIN.<br/>
When windows is booted they can log in with a local user account.<br/>
From here they have no admin permission and cant modify system files.<br/>
Everything is great!
<br/></p>
<h2>The problem</h2>
<p>My concern is when they boot their PC like they normally would and connect the USB device to their own Windows session.<br/>
They are prompted to type a PIN (since the file system is encrypted), but unfortunately this PIN is known because they need is to boot from USB.<br/>
From here they can access and modify ALL the system files !!<br/>
<br/>
<br/>
<strong>So my question is:</strong><br/>
How can we make sure that a user without admin permission can't access the system files?</p>
| 0non-cybersec
| Stackexchange |
First pc build, are parts ok? Clearance issues, dimensions, etc.. I already got the graphics card, Asus RTX 2070 Rog Strix, I'm about to get the rest. I need mostly confirmation that the dimensions, clearance for parts have no problems. I would also like to know if there are better parts I could get that won't change the price too much. Thanks
https://pcpartpicker.com/list/hxwqsk | 0non-cybersec
| Reddit |
Someone else posted their stoned drawing so I thought I’d share. Here’s “The Woods”. | 0non-cybersec
| Reddit |
AttributeError: 'datetime' module has no attribute 'strptime'. <p>Here is my <code>Transaction</code> class:</p>
<pre><code>class Transaction(object):
def __init__(self, company, num, price, date, is_buy):
self.company = company
self.num = num
self.price = price
self.date = datetime.strptime(date, "%Y-%m-%d")
self.is_buy = is_buy
</code></pre>
<p>And when I'm trying to run the <code>date</code> function:</p>
<pre><code>tr = Transaction('AAPL', 600, '2013-10-25')
print tr.date
</code></pre>
<p>I'm getting the following error:</p>
<pre><code> self.date = datetime.strptime(self.d, "%Y-%m-%d")
AttributeError: 'module' object has no attribute 'strptime'
</code></pre>
<p>How can I fix that?</p>
| 0non-cybersec
| Stackexchange |
What does COLLATE LOCALIZED ASC stand for?. <pre><code>private Cursor getContacts()
{
// Run query
Uri uri = ContactsContract.Contacts.CONTENT_URI;
String[] projection = new String[] {
ContactsContract.Contacts._ID,
ContactsContract.Contacts.DISPLAY_NAME
};
String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" +
(mShowInvisible ? "0" : "1") + "'";
String[] selectionArgs = null;
String sortOrder = ContactsContract.Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC";
return managedQuery(uri, projection, selection, selectionArgs, sortOrder);
}
</code></pre>
<p>What does <code>COLLATE LOCALIZED ASC</code> stand for?</p>
| 0non-cybersec
| Stackexchange |
Double whammy on a KTLA5 post. Context: man drives car into lake with wife and dog trapped in it.. | 0non-cybersec
| Reddit |
Nearby planetary system is seriously screwed up. | 0non-cybersec
| Reddit |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
Cheaters’ social network Ashley Madison reportedly faces data breach. | 1cybersec
| Reddit |
Two different listings at the same time. <p>I would like to show two different pieces of listings at the same time in a slide. With the following code the second listing only shows up at the end, while I would like it to alongside with the line 'int y = 20':</p>
<pre><code>\begin{lstlisting}
int x = 10; @\pause@
int y = 20; @\pause@
int z = 42; @\pause@
\end{lstlisting}
\begin{overlayarea}{\linewidth}{.5cm}
\begin{onlyenv}<2->
\begin{lstlisting}
int next (int x)
\end{lstlisting}
\end{onlyenv}
\end{overlayarea}
</code></pre>
<p>The delimiters @ are used to escape inside a listing block.</p>
| 0non-cybersec
| Stackexchange |
Terminal crashes when running lsblk -h. <p>Im currently running Ubuntu 14.04 LTS. In the desktop I open a terminal window and type:</p>
<pre><code>lsblk -h
</code></pre>
<p>And the terminal crashes! <code>lsblk</code> on its own runs fine. <code>lsblk --help</code> also crashes the terminal. If I try the command when SSH into the computer it runs fine. Does any one know how to resolve this problem?</p>
<p><code>env</code> also crashes the terminal. However, if I use SSH the <code>env</code> output is:</p>
<pre>
user1@user1:~$ env
XDG_SESSION_ID=4
TERM=vt220
SHELL=/bin/bash
XDG_SESSION_COOKIE=023a11a7ff65de4d4b3e1ed65489b4ff-1424963871.263960-1910753503
SSH_TTY=/dev/pts/16
USER=user1
LS_COLORS=
MAIL=/var/mail/user1
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
QT_QPA_PLATFORMTHEME=appmenu-qt5
PWD=/home/user1
LANG=en_GB.UTF-8
SHLVL=1
HOME=/home/user1
LANGUAGE=en_GB:en
PYTHONPATH=/home/user1/
LOGNAME=user1
LESSOPEN=| /usr/bin/lesspipe %s
XDG_RUNTIME_DIR=/run/user/1000
LESSCLOSE=/usr/bin/lesspipe %s %s
_=/usr/bin/env
</pre>
| 0non-cybersec
| Stackexchange |
Springtime in japan. | 0non-cybersec
| Reddit |
Why was the virtualbox package removed from the 14.04 repository?. <p>I'm having some problems trying to run my Windows XP virtual machine after upgrading to Ubuntu 14.04 today. When I tried to start it a message dialog was displayed saying that the kernel drivers aren't installed, in concrete they should be provided by a packaged named <code>virtualbox-dkms</code>. I decided to reinstall <code>virtualbox</code> so dependencies will get auto resolved, but the execution of command (<code>sudo apt-get install --reinstall virtualbox</code>) resulted in a message similar to: "cannot reinstall package because the package cannot be downloaded" (I'm reproducing the message by memory).</p>
<p>Then I tried using synaptic package manager gui. The package <code>virtualbox</code> and its dependencies are there, but without version number or description. Then I switched to main servers, and tried to update, now the package isn't even there anymore.</p>
<p>It may be a problem with my sources.list file but also may be that for some reason I don't know they decide to remove <code>virtualbox</code> from repository.</p>
<p>I think I will try to download the packages from the virtual box site for now but in Ubuntu I always installed virtualbox from repository.</p>
| 0non-cybersec
| Stackexchange |
i am thinking of quitting Facebook. People who don't use Facebook/social media how has your life been changed?. Is it a good decision? | 0non-cybersec
| Reddit |
General question about Integrals. <p>This might be a very very basic question but it would be kind if you could help me anyway:</p>
<p>Why is <span class="math-container">$-x^{2n}e^{-x^2/2}\Bigg|^{+\infty}_{-\infty}=0$</span></p>
<p>Is it because <span class="math-container">$\lim_{x\rightarrow \infty}(-x^{2n}e^{-x^2/2})=\lim_{x\rightarrow -\infty}(-x^{2n}e^{-x^2/2})$</span> and therefore:</p>
<p><span class="math-container">$$
\lim_{x\rightarrow \infty}(-x^{2n}e^{-x^2/2})-\lim_{x\rightarrow -\infty}(-x^{2n}e^{-x^2/2})=\lim_{x\rightarrow \infty}(-x^{2n}e^{-x^2/2})-\lim_{x\rightarrow \infty}(-x^{2n}e^{-x^2/2})=0?
$$</span></p>
| 0non-cybersec
| Stackexchange |
D-Rose Returning? He releases NEW Adidas Rose 3 Lows (Photo). | 0non-cybersec
| Reddit |
[EU] While fighting in the trenches, your fellow soldier just did the unthinkable - he pulled out his wand.. | 0non-cybersec
| Reddit |
OH MY GAH! It's so cheap!!1!1!. | 0non-cybersec
| Reddit |
Homogeneous Poisson Process Questions. <p>Assume that when the German plays Hungary in soccer, each team scores independently as a homogeneous Poisson process with rates $\lambda (\text{Germany}) = 1$ and $\lambda(\text{Hungary}) = 3$ goals per game. </p>
<p>a) Expected number of total goals in a single game. </p>
<p>b) Expected number of total goals scored in the first half, given that $2$ total goals were scored in the entire game. </p>
<p>c) Expected number of goals Germany scored in the entire game, given that $2$ total goals were scored in the first half. </p>
<p>What I really need help with is getting the formulas for parts b & c. I'm having difficulty forming what the Expectation formula should be.</p>
| 0non-cybersec
| Stackexchange |
Shovel and moon by Manu at Would Tattoo in Buenos Aires, Argentina. | 0non-cybersec
| Reddit |
China collapsing? Who knew.... | 0non-cybersec
| Reddit |
Tautology with Natural Deduction. <p>I'm trying to prove (p->q) v (q->p) is a tautology.
I need to start with an assumption, I would start with p->q or q->p but I always get stuck in the assumption. I don't find any way to get out of it to have a disjunction as a 'conclusion'. </p>
| 0non-cybersec
| Stackexchange |
Confusion regarding question came in my today's exam. <p>G(d) was determined to be $3d+c$, here c is :</p>
<ol>
<li>Constant of differentiation</li>
</ol>
<p>2.Constant of anti differentiation</p>
<p>3.constant of integartion</p>
<p>4.constant of death and taxes</p>
<p>I chose option 3. But i am confused between option 3 and 2. Is this question even right?</p>
<p>Thanks</p>
| 0non-cybersec
| Stackexchange |
The sound effects of The Thing are to me its most disturbing aspect - I haven't heard a lot of other creatures in film have such an otherworldly sound.. | 0non-cybersec
| Reddit |
Adding a second wifi router / wireless access point. <p>I have an existing wireless router setup and I want to add better coverage to a certain part of my house. The current wifi covers the area, but the signal is fairly weak and the throughput is commonly falls below what I can sustain through my cable modem.</p>
<p>I have pulled an ethernet cable through the walls, and I am considering just sticking a second access point on the end of it. Connect both ends to the LAN ports of the routers, give the new one a LAN address in the subnet, and it is on the network. Of course I will set the radio to use a different channel than the original access point.</p>
<p>My question is: Can I assign the same SSID to the second device and have the wireless clients auto-magically connect to the one with the best signal or I am better off giving them different SSIDs? Do I have to use <a href="http://en.wikipedia.org/wiki/Wireless_Distribution_System" rel="nofollow noreferrer">Wireless Distribution System (WDS)</a> of some sort even with the ethernet link between them?</p>
| 0non-cybersec
| Stackexchange |
group action on symmetric group. <p>Consider the action of <span class="math-container">$G=S_3$</span> on set <span class="math-container">$$A=\{(a,b)\,|\,a,b \text{ belongs to }\{1,2,3\} \text{ and } a \neq b \}$$</span> given by <span class="math-container">$g*(a,b)=(g(a),g(b)).$</span>Find the corresponding morphism. </p>
| 0non-cybersec
| Stackexchange |
Close ALL Chrome processes to allow channel-switch. <p>The Chrome browser can create a fairly large number of processes that are not necessarily closed when the browser is exited. For instance, if desktop notifications are enabled, various processes corresponding to different plugins that send notifications can be kept running indefinitely.</p>
<p>Unfortunately, this makes switching <a href="http://www.chromium.org/getting-involved/dev-channel" rel="nofollow noreferrer">build channels</a> tricky, because the installer for each channel needs all processes from the channel it's replacing to be closed. (This is not generally an issue for the Canary channel, since it doesn't usually <em>replace</em> another channel, but I expect that it will fail when switching from 32-bit Canary to 64-bit Canary). On Windows, since Google only recently released a "stable" 64-bit build, I expect quite a few people to be switching channels fairly soon.</p>
<p>Is there any easy way to close all Chrome processes before (or while) switching channels? The only way I've found is to manually close all Chrome processes, which seems like something I shouldn't need to do. I thought temporarily un-checking the "Continue running background apps when Google Chrome is closed" settings box might work, but that did not appear to stop everything. (It would be nice, of course, if the channel installers provided some sort of "suspend all Chrome activity" button or something, which could simply kill the processes since they're automatically restarted once Chrome is installed...)</p>
| 0non-cybersec
| Stackexchange |
TikZ inside TikZ-node with given text width does wrong positioning. <p>This code </p>
<pre><code>\documentclass{minimal}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\node[text width = 3cm]{
a a a a a a a a a a a a a a a a a a a a\\
\tikz{\draw (0,0) node {A} -- (1,0) node {B};}\hspace*{10cm}\\
a a a a a a a a a a a a a a a a a a a a
};
\end{tikzpicture}
\end{document}
</code></pre>
<p>gives this result:</p>
<p><a href="https://i.stack.imgur.com/mgEw8.png" rel="noreferrer"><img src="https://i.stack.imgur.com/mgEw8.png" alt="Result"></a></p>
<p>It places the line between A and B on the right of B and not between A and B.
Somehow specifying text width in the outer node confuses TikZ when it places the inner line.
How can I make it act normally such that the line is between A and B where it should be?</p>
| 0non-cybersec
| Stackexchange |
Homemade Scarecrow. | 0non-cybersec
| Reddit |
Paragraph style footnotes in plain XeTeX. <p>I’m trying to get footnotes set in the paragraph style in plain XeTeX. I’ve pasted the code from <code>fnpara.tex</code> into the preamble of my document and changed the fonts used in the actual footnotes to Palatino Linotype by pasting:</p>
<pre><code>\font\footnumberfont="Palatino Linotype:mapping=tex-text" at 8pt
\font\footnotesize="Palatino Linotype:mapping=tex-text" at 8pt
</code></pre>
<p>after the code from `fnpara'. The main font in my document is set like this:</p>
<pre><code>\font\pala="Palatino Linotype:+onum,mapping=tex-text" at 10pt
</code></pre>
<p>I call it by putting `\pala' at the start of the text. Everything works fine except for one thing: the superscript footnote reference numbers in the text block are in Computer Modern (cmr7), which looks strange, since everything else is in Palatino. I’m new to plain (Xe)TeX.</p>
<p>minimum working example:</p>
<pre><code>%!TEX TS-program = xetex
%!TEX encoding = UTF-8 Unicode
\input eplain
\font\pala="Palatino Linotype:+onum,mapping=tex-text" at 10pt
PLACE CODE FROM "fnpara.tex" HERE
\font\footnumberfont="Palatino Linotype:mapping=tex-text" at 8pt
\font\footnotesize="Palatino Linotype:mapping=tex-text" at 8pt
\pala
Lorem\footnote{First footnote.} ipsum dolor sit amet,\footnote{Second footnote.
(Every once in a while a long footnote might occur, just to make things difficult.)}
consectetur adipisicing\footnote{Third footnote.} elit,
\bye
</code></pre>
<p>i put the MWE in the question; thanks Torbjørn T.</p>
| 0non-cybersec
| Stackexchange |
If you are not someone’s first choice, don’t even bother. Me and this woman had insane chemistry. She even told this to her new BF. She kept cheating on him with me, promising that once she wants a serious relationship instead of a casual one, she will come around. Spoiler alert: she did not. She had numerous chances to break it off and be with me.
She came clean to her BF, but still wants to keep me around “as a friend”. She wants to know me as a friend first. It’s clearer than the sky what we have is simply more than friendship. Not a conversation goes by without saying the exact same thing as the other and this is only probably the smallest indicator.
It’s clear to me I’m just a backup plan. I told her how I feel like a backup plan and she kept saying I’m not just that and I was an option and she didn’t want a serious relationship at the time, yada yada. In the end this is what I’m to her: a safety net. Someone she knows she can rely on in the end.
Even if we will have a chance to be together, I couldn’t shake this feeling. She could’ve been with me instead of him, but she didn’t want me. I don’t want to be with someone as some consolation prize or backup plan. It’s degrading.
I know their relationship will fail but I have to be strong and decline when the opportunity arises.
Bottomline is if someone wants to be with you, even if the circumstances suck ass, will choose you. Anything else means they are emotionally fucked up or you are just a backup plan who they know will always be there. I tried to rationalize and justify her behaviour for a long time, but there isn’t. She just used me until she had enough. | 0non-cybersec
| Reddit |
How do I add a flag to an alias?. <p>Is it possible to add a flag to a <em>bash</em> alias you create yourself? e.g.</p>
<pre><code>con -a = 'ssh [email protected]'
con -b = 'ssh [email protected]'
</code></pre>
| 0non-cybersec
| Stackexchange |
iTunes on Windows Refuses to Upgrade. <p>I've been having a problem when trying to upgrade iTunes on Windows (7 x64). Every time I try to upgrade it, I get the error message:</p>
<blockquote>
<p>QuickTime was not found.</p>
<p>QuickTime is required to run iTunes. Please uninstall iTunes, then install iTunes again.</p>
</blockquote>
<p>Wanting to upgrade to 9.2 to get iOS4, I obliterated anything to do with Apple from my machine and reinstalled successfully, but this error comes back time and time again.</p>
<p>I recently found that <a href="http://ayende.com/Blog/archive/2010/08/16/frustration-thy-name-is-apple.aspx" rel="nofollow">I am not the only one suffering from this</a>.</p>
<p>Is there a way to solve this issue or am I doomed to stay like this forever?</p>
| 0non-cybersec
| Stackexchange |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
Royal Guard, Prisma Color Pencils, 8"x11". | 0non-cybersec
| Reddit |
How to escape back ticks. <p>MySQL requires tables that shadow reserved words to be back ticked. I have a table Role which is a reserved word, but I have already put my query in back ticks so I can write it over multiple lines (this is a toy query, large ones will not fit on one line).</p>
<p>How do I escape the back ticks?</p>
<p>Here is my code:</p>
<pre><code>dbmap := db.InitDb()
var roles []entities.Role
query :=
` << Difficult to see with SO's code editor widget, but here is a back tick
SELECT *
FROM `Role` <<< Needs escaping
` << Difficult to see, but here is a back tick
_, err := dbmap.Select(&roles, query, nil)
if err != nil {
panic(err)
}
fmt.Println(roles)
</code></pre>
| 0non-cybersec
| Stackexchange |
How do I see if Wi-Fi is connected on Android?. <p>I don't want my user to even try downloading something unless they have Wi-Fi connected. However, I can only seem to be able to tell if Wi-Fi is enabled, but they could still have a 3G connection.</p>
<pre><code>android.net.wifi.WifiManager m = (WifiManager) getSystemService(WIFI_SERVICE);
android.net.wifi.SupplicantState s = m.getConnectionInfo().getSupplicantState();
NetworkInfo.DetailedState state = WifiInfo.getDetailedStateOf(s);
if (state != NetworkInfo.DetailedState.CONNECTED) {
return false;
}
</code></pre>
<p>However, the state is not what I would expect. Even though Wi-Fi is connected, I am getting <code>OBTAINING_IPADDR</code> as the state.</p>
| 0non-cybersec
| Stackexchange |
I made a review of the often overlooked Fatal Frame/Project Zero: Maiden of Black Water. | 0non-cybersec
| Reddit |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
Is not having enough sex, a good enough reason to break up?. This recently happened to a buddy of mine.
They were together for about 2 years, and after countless of efforts from his side to talk about the lack of sex in their relationship (and things not changing) he decided to break up with her.
Now everyone thinks he's the bad guy, because everything else in their relationship was alright (ridiculous comments such as "he was just in it for the sex!")
I do agree with him though, sex is a very important part in a relationship, and if things don't change after bringing it up, etc. it's best to leave the relationship, as one person is unhappy and will just cause further frustration. | 0non-cybersec
| Reddit |
Translation of an argument in logical notation.. <p>I have to formulate the following argument into logical notation :</p>
<p><strong>All accused are guilty.All who are convicted will hang.Therefore if all who are guilty are convicted then all the accused will hang.</strong></p>
<p>Which I translated like this :</p>
<p>The premises are :</p>
<p>($\forall x)(Ax \rightarrow Gx)$.</p>
<p>($\forall x)(Cx \rightarrow Hx)$.</p>
<p>The conclusion is:</p>
<p>($\forall x)(Gx \rightarrow Cx) \rightarrow ((\forall y)(Ay \rightarrow Hy))$.</p>
<p>Is it a right translation ?
Thank you.</p>
| 0non-cybersec
| Stackexchange |
How to use spot instance with amazon elastic beanstalk?. <p>I have one infra that use amazon elastic beanstalk to deploy my application.
I need to scale my app adding some spot instances that EB do not support.</p>
<p>So I create a second autoscaling from a launch configuration with spot instances.
The autoscaling use the same load balancer created by beanstalk.</p>
<p>To up instances with the last version of my app, I copy the user data from the original launch configuration (created with beanstalk) to the launch configuration with spot instances (created by me).</p>
<p>This work fine, but:</p>
<ol>
<li><p>how to update spot instances that have come up from the second autoscaling when the beanstalk update instances managed by him with a new version of the app?</p>
</li>
<li><p>is there another way so easy as, and elegant, to use spot instances and enjoy the benefits of beanstalk?</p>
</li>
</ol>
<p><strong>UPDATE</strong></p>
<p>Elastic Beanstalk add support to spot instance since 2019... see:
<a href="https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html" rel="nofollow noreferrer">https://docs.aws.amazon.com/elasticbeanstalk/latest/relnotes/release-2019-11-25-spot.html</a></p>
| 0non-cybersec
| Stackexchange |
Apache Request Header Read Timeout (Reverse Proxy). <p>I keep seeing this in my apache 2.2.22 (Ubuntu) log files and don't know why it is occurring or how to fix it</p>
<pre><code>[debug] ssl_engine_kernel.c(1884): OpenSSL: Write: SSL negotiation finished successfully
[info] [client 10.0.0.5] Connection closed to child 3 with standard shutdown (server example.com:443)
[info] [client 10.0.0.5] (70007)The timeout specified has expired: SSL input filter read failed.
</code></pre>
<p>I've seen this already:
<a href="https://serverfault.com/questions/272083/apache-proxy-timeout">Apache Proxy TimeOut </a></p>
<p>I've tried a2dismod reqtimeout_module and these options as well:</p>
<pre><code> SetEnv proxy-sendchunks
SetEnv force-proxy-request-1.0 1
SetEnv proxy-nokeepalive 1
ProxyPass / https://example.com/ connectiontimeout=300 timeout=300
</code></pre>
<p>Apache Info:</p>
<pre><code># apachectl -V; apachectl -M
Server version: Apache/2.2.22 (Ubuntu)
Server built: Jul 12 2013 13:37:10
Server's Module Magic Number: 20051115:30
Server loaded: APR 1.4.6, APR-Util 1.3.12
Compiled using: APR 1.4.6, APR-Util 1.3.12
Architecture: 64-bit
Server MPM: Prefork
threaded: no
forked: yes (variable process count)
Server compiled with....
-D APACHE_MPM_DIR="server/mpm/prefork"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_SYSVSEM_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=128
-D HTTPD_ROOT="/etc/apache2"
-D SUEXEC_BIN="/usr/lib/apache2/suexec"
-D DEFAULT_PIDLOG="/var/run/apache2.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_LOCKFILE="/var/run/apache2/accept.lock"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="mime.types"
-D SERVER_CONFIG_FILE="apache2.conf"
Loaded Modules:
core_module (static)
log_config_module (static)
logio_module (static)
mpm_prefork_module (static)
http_module (static)
so_module (static)
alias_module (shared)
auth_basic_module (shared)
authn_file_module (shared)
authz_default_module (shared)
authz_groupfile_module (shared)
authz_host_module (shared)
authz_user_module (shared)
autoindex_module (shared)
cgi_module (shared)
deflate_module (shared)
dir_module (shared)
env_module (shared)
headers_module (shared)
mime_module (shared)
negotiation_module (shared)
proxy_module (shared)
proxy_http_module (shared)
reqtimeout_module (shared)
rewrite_module (shared)
security2_module (shared)
setenvif_module (shared)
ssl_module (shared)
status_module (shared)
unique_id_module (shared)
Syntax OK
# cat /etc/apache2/sites-available/scl/example.com
<Virtualhost *:80>
Servername example.com
Redirect / https://example.com/
</VirtualHost>
<VirtualHost *:443>
Servername example.com
SSLEngine on
SSLProxyEngine On
ProxyRequests Off
LogLevel Debug
DocumentRoot "/var/www/html/scl/trail"
ErrorLog "/var/log/apache2/trail-error_log"
CustomLog "/var/log/apache2/trail-error_log" common
DirectoryIndex index.html index.htm
<Directory /var/www/html/scl/trail>
Order deny,allow
Allow from all
SetHandler default-handler
</Directory>
ProxyPass / https://example.com/ connectiontimeout=300 timeout=300
ProxyPassReverse / https://example.com/
ProxyPreserveHost On
###################
# SSL Constraints #
###################
SSLProtocol -ALL +SSLv3 +TLSv1
# Choose cipher suites
SSLHonorCipherOrder On
SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:!LOW:!SSLv2:!EXPORT
# SameOrigin The page can only be displayed in a frame on the same origin as the page itself
Header set X-Frame-Options SAMEORIGIN
SSLCertificateFile /etc/apache2/example.com.crt
SSLCertificateKeyFile /etc/apache2/example.com.key
SSLCertificateChainFile /etc/apache2/gd_bundle.crt
SetOutputFilter INFLATE;proxy-html;DEFLATE
</VirtualHost>
</code></pre>
| 0non-cybersec
| Stackexchange |
Become Cyber Security Expert and Ethical Hacker. This Course is specially designed to enhance your Hacking Capabilities.. | 1cybersec
| Reddit |
Untitled
A SEARCH FOR Λb IN π−-A COLLISIONS AT 515 GeV/c
BY
FRANCISCO JAVIER VACA-ALVAREZ
B.S., Universidad Michoacana, Morelia, Michoacán, México, 1989
M.S., University of Illinois at Chicago, 1992
THESIS
Submitted as partial fulfillment of the requirements
for the degree of Doctor of Philosophy in Physics
in the Graduate College of the
University of Illinois at Chicago, 1995
Chicago, Illinois
UICHEP-95/011-E
iii
This thesis is dedicated to my wife Maria Del Carmen
Montes de Vaca and to my son Francisco Javier Vaca Jr. for
their love and support, and to my parents, Mariano and
Consuelo Vaca, without whom it would never have been
accomplished.
Francisco Javier
iv
ACKNOWLEDGMENTS
I am pleased to have the opportunity to thank everyone who contributed to my
education of more than twenty years. I begin by thanking God, who has always looked
after me. Second, my parents, whom with many sacrifices put me through college and the
beginning of graduate school. Also to my spouse Carmen, that has been very supportive,
loving, and caring. Thank you Carmen. Next, my son Paquito, I guess if it had not been
for him, writing this thesis would have not been half as fun. Every night, while I was in
front of the computer typing or working on this thesis, he would approach me and say in
Spanish: “quiero trabajar” (I want to work). So I would sit him in my lap and let him type.
Thank you Paquito for helping me type my thesis and for making me type parts of it more
than once. I also thank all my family for supporting me when I most needed them.
My formation as a physicist I owe to several Professors. The first one to thank is
my advisor Prof. Seymour Margulies, who passed away May 4, 1995. He was not only
the best physics teacher I have ever had, but a role model as a physicist. Thank you Sy,
wherever you are. I thank Prof. Howard Goldberg for taking over what Prof. Margulies
began. He has friendlily helped me throughout my thesis project. His support, advice,
and encouragement in the last few months were much appreciated in a very difficult time.
Thank you Howard. I also thank Prof. Julius Solomon, he has been very supportive and
helpful during my training as graduate student. Thank you Julius. The members of the
E672 collaboration deserve special thanks for teaching me much of what I know about
experimental high energy physics. I thank Prof. Andrzej Zieminski, E672 spokesman,
v
who supported my work as a member of the collaboration and always had confidence in
me. To Dr. Hector Mendez and Dr. Richard Jesik, I owe more than thanks. Both of them
have been very helpful throughout my years as a member of E672. Thank you Hector and
Ricky. To the rest of the E672 collaboration, Prof. Loretta Dauwe, Dr. Andrei Gribushin,
Dr. Victor Koreshev, Dr. Victor Abramov, Dr. Rui Li, and all the others whom I have not
mentioned, thank you for being my colleagues. I also want to thank all of my colleagues
from our sister experiment E706. In particular, I thank Dr. George Ginther for all his
helpful comments about my studies in E672. “Mil gracias” (One thousand thanks) to the
E672 and E706 collaborations for putting together such wonderful experiments.
I also thank all my Professors and fellow students at the UIC physics department.
Prof. Wee Y. Kung, Prof. Clive Halliwell, Prof. Pagnamenta, Mark Oram, Salima Yala,
Thomas Mckibben, and the list continues ....Thank you every one.
Francisco Javier
vi
TABLE OF CONTENTS
CHAPTER PAGE
1. INTRODUCTION ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.1 Theoretical overview... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.1.1 Hadroproduction of b quarks.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
1.1.2 Fragmentation of b quarks .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.1.3 b-hadron decay .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.2 Evidence for the existence of the Λb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.3 Previous searches for the Λb → J/ψ Λ
0
decay channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.4 Analysis objective .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2. THE MWEST SPECTROMETER ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1 Overview of the detector.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2 Beam... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.1 Beam line.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.2 Cerenkov counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3 Hadron shield and veto walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4 Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5 Upstream tracking system... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5.1 Silicon-strip detector system... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.5.2 Dipole magnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.3 Upstream proportional wire chambers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.6 Muon system... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.6.1 Upstream muon proportional wire chambers .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.6.2 Toroid .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.6.3 Muon pretrigger hodoscopes .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.6.4 Downstream muon proportional wire chambers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
vii
3. DATA ACQUISITION SYSTEM... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.1 Overview of the data acquisition system... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2 Muon system readout .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.1 Muon pretrigger hodoscope readout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.2 Upstream muon proportional wire chamber readout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2.3 Dimuon trigger processor .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3 Dimuon trigger.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4. EVENT SELECTION AND RECONSTRUCTION... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.1 Event selection.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.1.1 Dimuon preselection .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.2 Event reconstruction .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.2.1 Track finding .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.2.2 Track linking.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.2.3 Vertex finding .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.3 Characteristics of reconstructed dimuon events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5. THE J/ψ → µ+ µ- SAMPLE ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.1 Selection of the J/ψ → µ+ µ- sample .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
6. THE Λ0 → p π- (AND CHARGE CONJUGATE) SAMPLE... . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
6.1 Reconstruction algorithms for the Λ0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
6.1.1 Reconstruction near the target/SSDs region.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.1.2 Reconstruction in the region upstream of the dipole magnet. . . . . . . . . . . . . . . . . . . . 74
6.1.3 Reconstruction inside the dipole magnet region .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.2 The K0s → π
+ π- signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
6.2.1 The K
0
s → π
+ π- signal in the region near the target/SSDs .. . . . . . . . . . . . . . . . . . . . 83
6.2.2 The K
0
s→ π
+π- signal in the regions upstream and inside the dipole magnet 85
6.2.3 Distinguishing the Λ0 → p π- (and charge conjugate) decays from the K0s →
π+ π- decays.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
7. THE Λb→ J/ψ Λ
0
DECAY CHANNEL... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.1 The Λb→ J/ψ Λ
0
Monte-Carlo simulation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
viii
7.2 The Λb→ J/ψ Λ
0
search method and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
8. EVALUATION OF THE Λb→ J/ψ Λ
0
PRODUCTION RATE ... . . . . . . . . . . . . . . . . . . . . . . .111
8.1 Acceptances and efficiencies .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111
8.2 Upper limit on the Λb production rate.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
9. CONCLUSIONS... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120
APPENDIX A ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
APPENDIX B ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
APPENDIX C ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
REFERENCES ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140
VITA ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
ix
LIST OF TABLES
TABLE PAGE
I . The Quarks.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
II. The Leptons.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
III. The Gauge Bosons.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
IV. Feynman diagrams of Typical Interactions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
V. Results on Λ
0
-lepton and Λc
+-lepton correlations in Z
0
decays at LEP.
The first uncertainty is statistical and the second is systematic.. . . . . . . . . . . 19
VI. Results from other searches for the Λb → J/ψ Λ
0
decay channel . . . . . . . . 20
VII. Upstream muon PWC specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
VIII. Downstream muon PWC specifications.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
IX Summary of the number of Λ
0
(and Λ0 ) candidates that survived each
cut employed to select the sample used to search for the Λb → J/ψ Λ
0
decay.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
X. The total detection efficiencies for the different particles, which are the
products the kinematical and geometrical acceptance, reconstruction
efficiencie and preselection efficiencie. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
x
LIST OF FIGURES
FIGURES PAGE
1.1. Lowest-order QCD subprocess producing QQ heavy quark pairs.. . . . . 9
1.2. The bb total cross-section for π−N collisions as measured by
references. [22], [23], [24], and [11], and the theoretical prediction by
Berger [20] and MNR [21]. The uncertainties shown for the measured
values are the statistical and systematic contributions added in
quadrature.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3. Schematic picture of fragmentation in which breaking of the lines of
the color force between the separating heavy quarks of a QQ pair
produce a light qqqq diquark pair which combines with the heavy
quarks to form a heavy baryon pair.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.4. Feynman diagrams for the non-leptonic decay of a b hadron.. . . . . . . . . . . . 15
1.5. The Λb → Λ
0 l Xl
− ν decay channel quark diagram... . . . . . . . . . . . . . . . . . . . . 19
1.6. The Λb → J/ψ Λ
0
decay channel quark diagram. .. . . . . . . . . . . . . . . . . . . . . . . . . 20
2.1. The physical layout of the MWEST spectrometer.. . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2. The physical layout of the target and SSD system ... . . . . . . . . . . . . . . . . . . . . . . 27
2.3. The physical layout of the muon spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.4. The schematic view of the muon pretrigger hodoscopes.. . . . . . . . . . . . . . . . . 34
xi
2.5. Downstream muon proportional wire chamber: (a) physical
dimensions; (b) cross section of the chamber; (c) cutaway view of the
chamber .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.1. Diagram of the MWEST detector data acquisition system .. . . . . . . . . . . . . . . 39
3.2. Schematic diagram of the dimuon trigger processor.. . . . . . . . . . . . . . . . . . . . . . 43
4.1. Illustration showing the first roads used in the track algorithm and the
scheme to subdivide a road into other roads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2. Illustration of a simple example of the track finding algorithm, the
arrow shows the muon track.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.3. SSD-PWC linking scheme... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.4. The fractional uncertainty of momentum vs. momentum for fully
linked muon tracks.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4.5. Distribution of the primary vertices found in the “PSI” sample for
those dimuon events that are tagged as J/ψ s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.6. Transverse impact-parameter of the SSD-PWC linked tracks with the
primary vertex, for events in the “PSI” sample... . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.7. Invariant-mass spectrum of the opposite sign muon pairs . . . . . . . . . . . . . . . . 58
4.8. Invariant-mass spectrum of the opposite sign muon pairs in the J/ψ
region. The solid line is a fit to the data.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.9. Invariant-mass spectrum of J/ψ π
+
π− combinations. The solid line is
a fit to the data .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
xii
4.10. Invariant-mass spectrum of J/ψ γ combinations for converted γ s. The
solid line is a fit to the data.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.11 (a) A comparison of our measurements of the fraction of inclusive J/ψ
yield due to ψ(2S), χ1, χ2, and directly produced J/ψ s, to the
fractions predicted by the color evaporation model [47]; and (b) to the
fractions predicted by the color singlet model [48]. . . . . . . . . . . . . . . . . . . . . . . . . 63
4.12. Combined invariant-mass spectrum for B
±
→ J/ψ K± and B0 → J/ψ
K
0*
(hatched).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.1. The dimuon invariant-mass distribution for the “PSI” sample. The
solid line is a fit to the data that includes the Monte-Carlo resolution
functions for the J/ψ and ψ(2S), and two exponential functions for the
background .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.1. Regions in the spectrometer where Λ
0
s can be reconstructed. . . . . . . . . . . . 70
6.2. The illustration shows the topology of a Λ
0
→ p π− decaying near the
target/SSD region .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.3. Invariant-mass distribution using only SSD-PWC tracks for p π
−
(and
p π+) track combinations intercepting in the target/SSDs region. The
solid line is a fit to the data.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.4. Illustration of the proton and pions PWC tracks, for those Λ
0
s that
decayed in the region upstream of the dipole magnet. The solid lines
are the reconstructed PWC tracks .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.5. The illustration shows the topology of a Λ
0
→ p π− decay, and the
definition of relative pT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
6.6. Distribution of minimum relative pT for tracks intersecting upstream of
xiii
the dipole magnet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
6.7. Invariant-mass distribution using only PWC tracks for p π
− (and p π+)
combinations for tracks intercepting in the region upstream of the
dipole magnet. The solid line is a fit to the data.. . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.8. Illustration of the proton and pion PWC tracks, for those Λ
0
s that
decayed in the region inside the dipole magnet. The solid lines are the
reconstructed PWC tracks.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.9. Distribution of minimum relative pT for tracks intersecting inside the
dipole magnet.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
6.10. Invariant-mass distribution using only PWC tracks for p π
−
(and p π+)
combinations for tracks intercepting in the region inside the dipole
magnet. The solid line is a fit to the data.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
6.11. Invariant-mass distribution using only SSD-PWC tracks for π
+
π−
track combinations intercepting in the target/SSDs region. . . . . . . . . . . . . . . . 84
6.12. Invariant-mass distribution using only PWC tracks for π
+
π−
combinations for tracks intercepting in the region upstream of the
dipole magnet.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.13. Invariant-mass distribution using only PWC tracks for π
+
π−
combinations for tracks intercepting in the region inside the dipole
magnet.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
6.14 Podolanski-Armenteros plot for the K
0
s → π
+ π−, Λ0 → p π−, and Λ0
→ p π+ decays.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
6.15 Podolanski-Armenteros plot for the Λ
0
(and Λ0 ) candidates decaying
xiv
upstream the dipole magnet. These included all the combinations
between 1.105 GeV/c
2
and 1.125 GeV/c
2
in Figure 6.7. The lines are
the kinematical boundaries for the K
0
s → π
+ π−, Λ0 → p π−, and Λ0
→ p π+ decays (see previous Figure).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
6.16 Invariant-mass spectrum of p π
−
and pπ+ combinations that passed the
criteria of being a Λ0 decaying in the region upstream of dipole magnet
when both tracks are assigned pion masses. The solid line is the
expected distribution obtained from Monte-Carlo and the dots are from
data.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
6.17 Invariant-mass spectrum of p π
− and pπ+ combinations that passed the
criteria of being a Λ0 decaying in the region inside of dipole magnet
when both tracks are assigned pion masses. The solid line is the
expected distribution obtained from Monte-Carlo and the dots are from
data... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.1. Generated xF vs. pT
2 distribution of the b quark from Monte-Carlo
events.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.2 (a) Generated xF distribution of the b quark from Monte-Carlo events
(projection from the two-dimesional distribution); and (b) generated pT
2
distribution of the b quark from Monte-Carlo events (projection from
the two-dimesional distribution).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.3. Two-dimensional dimuon acceptance as a function of xF and pT
2 from
Λb→ J/ψ Λ
0
events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
7.4. Monte-Carlo and data distributions of the reconstructed track
multiplicity. The solid line represents the Monte-Carlo and the dots the
data.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
xv
7.5. Monte-Carlo and data distributions of the momenta of charged hadron
tracks. The solid line represents the Monte-Carlo and the dots the
data... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7.6. Monte-Carlo and data distributions of the pT of charged hadron tracks.
The solid line represents the Monte-Carlo and the dots the data... . . . . . . . 100
7.7. The reconstructed J/ψ signal after background subtraction, the solid
line is from Monte-Carlo and the dots are from data. The Monte-Carlo
is normalized to have the same number of events in the signal region as
the data .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
7.8. The reconstructed Λ
0
signal after background subtraction for those Λ0s
that decayed in the target/SSD region. The solid line is from Monte-
Carlo and the dots are from data. The Monte-Carlo is normalized to
have the same number of events in the signal region as the data . . . . . . . . . 103
7.9. The reconstructed Λ
0
signal after background subtraction for those Λ0s
that decayed upstream of the dipole magnet. The solid line is from
Monte-Carlo and the dots are from data. The Monte-Carlo is
normalized to have the same number of events in the signal region as
the data .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
7.10. The reconstructed Λ
0
signal after background subtraction for those Λ0s
that decayed inside the dipole magnet. The solid line is from Monte-
Carlo and the dots are from data. The Monte-Carlo is normalized to
have the same number of events in the signal region as the data. . . . . . . . . 105
7.11. The topology of the Λb → J/ψ Λ
0
decay .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
7.12. (a) Λ
0
-pT distribution from data, and (b) from the Λb→ J/ψ Λ
0
Monte-
Carlo.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
xvi
7.13. (a) The invariant mass for the J/ψ Λ
0 combinations; (b) the invariant
mass for the J/ψ Λ0 combinations from Monte-Carlo; (c) J/ψ Λ0
wrong frame background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
8.1 The invariant mass distribution (solid) for the J/ψ Λ
0 combinations,
without using the K
0
s mass cut, and the wrong-frame background
(dashed) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
8.2 The invariant-mass distribution for the J/ψ Λ
0 combinations, without
using the K
0
s mass cut, and requiring that the J/ψ s originate from
secondary vertices... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
A. 1. The χ
2
per degree of freedom distribution from the J/ψ refit. . . . . . . . . . . . . 131
A. 2. Residuals of the J/ψ momentum between the generated momentum
value in the Λb→ J/ψ Λ
0
Monte-Carlo and the reconstructed value.
The dashed line is for the values reconstructed by the initial track
finding. The solid line shows the residuals of the momentum after the
refit.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
A. 3. Residuals of the z-coordinate of the decay vertex between the value
generated in the Monte-Carlo and the value reconstructed. The dashed
line is for the values found by the initial track finding and the solid is
for those after the refit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
B. 1. The thin lens approximation is used to compute the momenta of the
proton and pion tracks of those Λ0 s that decayed upstream of the
dipole magnet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
C. 1. Circular trajectory described by of a proton or pion of a Λ0 that decays
inside the dipole magnet.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
xvii
SUMMARY
An extensive analysis was performed on 8.0 pb
-1
of dimuon data produced in π− A
collisions at 515 GeV/c to search for Λb events in the decay channel Λb → J/ψ Λ
0
, with
J/ψ → µ+ µ- and Λ0 → p π− (and for the conjugate reactions). The muon tracks from J/ψ
decays were refittedwith the mass constraint of two-body decay and with the constraint that
both muon tracks intersect at a common point. The Λ0 s were identified by their
characteristic decay, giving the large fraction of their momenta to the protons. Λ0 s were
reconstructed in three regions of the E672/E706 spectrometer, in the SSD/target region, in
the region between the SSDs and the dipole magnet, and inside the dipole magnet using an
iterating algorithm. Several cuts were applied to the Λ0 (and Λ0 ) to make a clean Λ0
(and Λ0 ) data sample. Among the cuts there was a K0s mass cut, in which if the Λ
0
(or
Λ0 ) had the mass of the K0s under the hypothesis of both tracks being π
+ π−, the Λ0
(or Λ0 ) candidates were rejected. These give a clean Λ0 (and Λ0 ) data sample of 575 ± 35
Λ0 (and Λ0 ) candidates.
To search for the Λb → J/ψ Λ
0
(and charge conjugate reaction), J/ψ s that passed
the muon refit were combined with Λ0 s (or Λ0 s) when they existed in the same event.
The results show 2 events in the Λb mass region. Using the E672 measurement of the bb
cross-section, and considering the 2 Λb event candidates as signal with zero background,
an upper limit to F(Λb) * Br(Λb → J/ψ Λ
0
) was found to be less than 6.2 x10
-2
at 90 %
xviii
C.L. An upper limit was also calculate without using a K
0
s mass cut for the Λ
0
s (and
Λ0 s), and then, requiring that the J/ψ s originate from secondary vertices, giving
F(Λb) * Br(Λb → J/ψ Λ
0
) < 3.1 x10
-2
at 90 % C.L and F(Λb) * Br(Λb → J/ψ Λ
0
) < 3.2
x10
-2
at 90 % C.L, respectively.
1
CHAPTER 1
1. INTRODUCTION
Since the discovery of the b quark in 1977 [1], much progress has been made in
measuring and understanding the properties of beauty particles; this is primarily true for the
Bu and Bd mesons, but not as much for the beauty baryons. The existence of Λb (bud), the
lightest of the baryons containing a b quark, has been somewhat controversial. In 1981,
experiment R415, which used the Split Field Magnet (SFM) detector at the Intersecting
Storage Ring (ISR) at CERN, reported an observation of the Λb through the decay channel
Λb → p D
0
π− [2] yielding a rest mass for the Λb of ( 5425 75
175
−
+ ) MeV/c2. Later, in 1982,
experiment R416, using an upgraded version of the R415 detector, performed the same
search for Λb → p D
0
π− with a negative result [3]. This led to some discussion by the
R415 collaboration claiming that experiment R416 did not have the necessary rejection
power against charged hadrons; therefore, it should not have been able to observe beauty
baryons at the ISR [4]. Further evidence for the Λb was reported in 1991 by the former
R415 collaboration in a second upgraded experiment, R422, at the ISR. Two different Λb
decay modes were observed: Λb → p D
0
π− and Λ Λb c→
+ + − −π π π [5]; the mass of the Λb
was found to be ( 5640 200
150
−
+ ) MeV/c2 and ( 5650 200
150
−
+ ) MeV/c2 for each mode, respectively. In
2
1986, an experiment using the Fermilab Multiparticle Spectrometer reported the observation
of a heavy baryon decaying into Λ0 0Ks π π π π
+ − + − and having an invariant mass of 5750
MeV/c2 [6]; however, this experiment did not claim to have observed the Λb. CERN
experiment UA1 reported in 1991 the discovery of the Λb decay channel Λb → J/ψ Λ
0
,
claiming a signal of 16 ± 5 events above a background of 9 ± 1 events [7]; they measured
the mass of the Λb to be (5640 ± 50 (stat) ± 30 (sys)) MeV/ c2. Since then, other
experiments have searched for this decay mode such as ALEPH and OPAL at CERN [8],
and CDF at Fermilab [9], however they have all failed to confirm UA1’s observation. In
1992, LEP experiments ALEPH, DELPHI, and OPAL reported evidence for the existence
of the Λb [10] through observation of the semi-leptonic decay channels Λb → Λ
0 l Xl
− ν
and Λb → Λc ll X
+ − ν in Z0 decays.
In the fixed-target experiment E672/E706 at Fermilab, we have measured the bb
total cross-section using our 1990 π− -A interactions at 515 GeV/c [11]. In addition we
observed exclusive decays of B hadrons such as B
±
→ J/ψ K± and B0 → J/ψ K0*[11].
This suggests us to search for the Λb → J/ψ Λ
0
decay mode, and to measure the product of
the production fraction F(Λb), times the branching ratio Br(Λb → J/ψ Λ
0
).
The remainder of this chapter involves a review of the basic concepts in particle
physics which are pertinent to the study of beauty baryons. It also presents detailed results
of previous experimental searches for the Λb.
3
1.1 Theoretical overview
Present evidence indicates that matter is built from two types of fundamental
particles called quarks and leptons, which are structureless and point-like on a scale of
10 17− m. Quarks carry fractional electric charge -e/3 or +2e/3, where e is the magnitude of
the electron charge, and have spin 1/2. They come in several different flavors labeled u
(up), d (down), s (strange), c (charm), b (bottom), and t (top). Each quark has it own
internal quantum numbers. The u and d quarks are grouped in an isospin doublet with I =
1/2, and with the third component I3 = +1/2 for the u and I3= -1/2 for the d. The s quark is
assigned an internal quantum number called strangeness, with value S = -1. The c quark is
assigned an internal quantum number called charm, with value C= +1. The b quark is
assigned the bottom quantum number B= -1, and the t quark is assigned the top quantum
number T = +1. Quarks also have a baryon number assigned to them, B
*
= 1/3 for quarks
and B
*
= -1/3 for the antiquarks, which is conserved in any interaction. Because of their
Table I. The Quarks.
Electric Charge Rest Mass a
u
doublet
d
s
b
c
t
2 - 8
176,000; 199,000
S = -1
C= +1
B =-1
T = +1
Symbol
Internal Quantum
Number
I3 = +
1
2
I3 = −
1
2
I =
1
2
+ 2
3
−
1
3
+ 2
3
−
1
3
+
2
3
−
1
3
5 -15
100 - 300
1000 - 1600
4100 - 4500
Q/e (MeV/c2)
a The quark masses are taken from Ref. [12], except the top
quark mass which is taken from Ref.[13] and [14].
4
masses, the u, d, and s quarks are referred to as light quarks and the c, b, and t as heavy
quarks. Table I shows the electric charges and masses for the six quarks along with their
internal quantum numbers. Each of the six quarks has its antiquark partner, which has the
opposite quantum numbers and the same rest mass.
The leptons carry integral charge, 0 or ± e, and have spin 1/2. The neutral leptons
are called neutrinos, and have very small (perhaps zero) rest masses. The leptons appear to
come in doublets, with each neutrino being assigned a subscript corresponding to its
charged partner. The three different types of charged leptons are known as the electron (e),
the muon (µ), and the tau (τ). Charged leptons are distinguished from antileptons by the
sign of their charges. The neutrinos are longitudinally polarized: they have their spins
opposite to their velocity vectors (left handed), while antineutrinos have spins in the same
direction (right handed). A lepton number Le, Lµ, and Lτ of +1 is assigned to each type of
lepton, respectively, and -1 to each type of antilepton. The lepton number is always
conserved in any interaction. The properties of the leptons are summarized in Table II.
Table II. The Leptons
Symbol Electric ChargeQ/e
Rest Massa
(MeV/c2) Antiparticle
e− −1 0.511 e +
ν
e 0 < 0.0051
µ− −1 105.6 µ +
ν
µ 0 < 0.27
τ− −1 1777.1 τ +
ν
τ 0 < 31
ντ
ν µ
νe
a The mass values are obtained from Ref. [12].
5
Quarks and leptons exist in three generations: The u, d, e
−,
and νe are the first
generation; the s, c, µ−, and νµ are the second generation; and the b, t, τ
−, and ντ are the
third generation. There are experimental measurements that indicate that there are only
three generations1.
Four fundamental forces (the gravitational, the electromagnetic, the weak, and the
strong) govern the interactions between quarks and leptons. The gravitational force is by
far the weakest of the four, and can be neglected for the study of interactions between
elementary particles at typical distances of the order of one femtometer. Thus, ignoring the
gravitational force, the charged leptons have electromagnetic and weak interactions, while
the neutrinos have only weak interactions. The quarks are subject to the electromagnetic,
weak, and strong interactions. The field quanta, or mediators, for the electromagnetic,
weak, and strong forces are the photon (γ ), the intermediate vector bosons W ± and Z0, and
1 See page 1333 of reference [12].
Table III. The Gauge Bosons
Force Field Quantum
Electric Charge Rest Massa
(GeV/c2)
Electromagnetic
Weak
Strong g
γ
W ±, Z0
0
±1, 0
0
< 3 x 10-27
80.22, 91.18
0
Q/e
a The values for the boson masses are obtained from Ref.[12].
6
the gluon (g), respectively. All of the field quanta have spin 1 and are called, in general,
gauge bosons. Table III summarizes the properties of the gauge bosons.
The electromagnetic force is described by the theory of Quantum Electrodynamics
(QED). Here, the sources of the field are the electric charges of the interacting particles.
The strength of the coupling constant of this force is called α and has a value of
approximately 1/137. In the case of the strong force, which is described by the theory
called Quantum Chromodynamics (QCD), quarks have an additional quantum number,
whimsically called color charge, which is the source of this interaction. Each quark can
have one of three primary color charges: red, green, or blue, denoted symbolically by R,
G, and B, respectively. The antiquarks have, in similar fashion, color charges denoted by
R,G,and B. Just as electric charge is conserved, so is color charge. Gluons also carry the
strong-field color charge. They are bicolored objects and can be of eight different
color/anti-color combinations1:
RB RG BG BR GR GB
RR BB RR BB GG
, , , , , , ,
− + −
2
2
6
and .
Quarks combine to form colorless particles (color singlets) called hadrons, which are
strongly interacting particles. In practice, we cannot observe isolated quarks or gluons;
instead, we observe hadrons. The quark and gluon constituents of hadrons are generally
known as partons. Hadrons that contain qq valence quarks are called mesons, and those
1With three colors and three anti-colors one expects 32=9 combinations, but one of these is
a color singlet and must be excluded.
7
that contain qqq (or qqq ) valence quarks are called baryons. The coupling constant of the
strong interactions is called αs and it depends on the momentum transfer Q
2
in a given
reaction. Thus, αs is said to be a running coupling constant.
α
π
s
f
QCD
n
Q
Q
2
2
2
12
33 2
( ) =
−( )
log Λ
;
where nf is the number of flavors, ΛQCD is a parameter to be determined by experiment.
Therefore, if the nf = 5 threshold is at Q
2
= (2 mb)
2
= 100 GeV
2
, and with ΛQCD = Λ5 =
0.2 GeV, then αs is equal to 0.48.
The weak force is described by the electroweak theory developed by Weinberg and
Salam in the late sixties [15]. This gauge theory unifies the electromagnetic and weak
interactions. The source of the weak force is a property called the weak charge, which
gives quarks and leptons flavor-changing transitions. The corresponding effective
coupling constant is called the Fermi constant, and has a value of GF =1.2x10
-5 GeV-2.
The fundamental electroweak coupling constant, called gW, is related to GF through
g M GW W F
2 8 2/ /= , where MW is the mass of the W boson.
8
The above brief introduction to quarks and leptons and the interactions among them
is the modern view of fundamental particles and forces known as the Standard Model.
Table IV illustrates Feynman diagrams1 of typical interactions in the Standard Model.
1 For a description of how to read and construct Feynman diagram see Ref. [16].
Table IV. Feynman diagrams of Typical Interactions.
Interaction Charge Quarks Leptons
uB
uR
Strong Color
Electromagnetic Electric charge (e)
Weak
Weak charge(gW),
giving u -> d or νe -> e−
flavor-changing
transions
u
u
e−
e−
u
d
νe
e−
g
γ
W+
W+
γ
RB
9
1.1.1 Hadroproduction of b quarks
The hadronic production of b quarks is fundamental for the study of perturbative
quantum chromodynamics (QCD) since results may be used to test and constrain the
current form of the theory. The cross-sections for open-flavor (i.e., unbound) production
of heavy quark pairs ( QQ ) are predicted by QCD. The lowest-order parton subprocesses
are quark-antiquark fusion and gluon-gluon fusion, illustrated in Figure 1.1.
The hadron-hadron ( h h QQ X1 2 → ) production cross-section for heavy quark pairs
is expressed as convolution of the parton-parton scattering cross-sections, ˆ ,σ i j , with the
distribution function of the partons, summed over all partons:
g qQ
q
g
g
g
g
g
Q
Q
Q
Q Q
Q
Q
Figure 1.1. Lowest-order QCD subprocess producing QQ heavy quark pairs.
10
σ σS m Q dx dx f x Q f x Q s m Q
m
x S
m
S
i j
i j i j, , , , ˆ ˆ, ,
,
,
2
1 2
4
1
4
1
1
2
2
2 2
2
1
2
( ) = ( ) ( ) ( )∫∫∑ , ( 1.1)
where S is the square of the total center-of-mass energy in the hadron-hadron system, m is
the mass of the heavy quark, and Q
2
is the mass factorization scale. The i and j indices run
over all partons (quarks, antiquarks, and gluons) in the hadrons h1 and h2, respectively.
The variable x1 is the fractional four-momentum vector of the parton in hadron h1, and x2
is that of the parton in hadron h2. Thus, in the parton-parton system the square of the
center-of-mass energy is ŝ x x S≈ 1 2 . f x Qi 1
2,( ) dx1 is equal to the probability that parton i
in hadron h1 carries a fraction x1 of S , analogously, f x Qj 2
2,( ) dx2 for parton j in hadron
h2. These parton densities are empirically determined from electron and neutrino deep-
inelastic scattering (see Ref. [17]), and the parton-parton scattering cross-section,
ˆ ˆσ i j s m Q, , ,
2( ), can be calculated in perturbative QCD [18].
The partonic cross-sections in a next-to-leading-order (NLO) or O sα
3( ) power-
series expansion are usually written in terms of so-called scaling ratios as
ˆ ˆ, , ln, , , ,σ
α
η πα ηi j
s
i j s i j i js m Q
m
f f f
Q
m
2 2
2
2
0 1 1
2
24( ) = ( ) + ( ) +
( ) ( ) ( ) , ( 1.2)
where η = −
ŝ
m4
1
2
or η =
4 2m
ŝ
. The dimensionless functions fi j,
( )( )0 η and fi j,
( )( )1 η
represent the Born approximation and the O(αs) corrections, respectively, and fi j,
( )( )1 η
appears when the mass factorization scale, Q
2
, deviates from the square of the heavy flavor
11
quark mass, m2 . NLO calculations of the partonic cross-sections have been computed by
Nason, Dawson, and Ellis (NDE) [19]. The bb total cross-section for hadron-hadron
collisions at current fixed-target energies has been calculated to NLO using NDE results by
Berger [20], and also by Mangano, Nason, and Rodolfi (MNR) [21]. Experimentally, the
bb total cross-section has been measured at fixed-target energies by experiments WA78
[22] and NA10 [23] at CERN and E653 [24] and E672/E706 [11] at Fermilab; Figure 1.2
shows the results for π−N collisions and also the theoretical predictions of Berger and
MNR for several different mass factorization scales, Q
2
, and heavy-flavor quark masses,
mb . It is important to mention here that in hadron-hadron collisions at collider energies
such as that in CDF and D0 ( s = 1800 GeV) the bb total cross-section is three orders of
magnitude larger than at our fixed-targert energies [25].
12
E672/E706 (Fermilab) [11]
E653 (Fermilab) [24]
WA78 (CERN) [22]
NA10 (CERN) [23]
1
10
100
150 250 350 450 550 650
Plab (GeV/c)
(a)
(b)
(c)
(d)
(b) MNR (Q2 = , = 4.5 GeV) [21]
(c) Berger (Q2 = , = 5.0 GeV) [20]
(d) MNR (Q2 = 4 , = 5.0 GeV) [21]
m b
2
mb
2
mb
2
m b
2
mb
mb
mb
mb
750
(a) MNR (Q2 = /4, = 4.5 GeV) [21]
σ
(
n
b
/n
u
cl
eo
n
)
Figure 1.2. The bb total cross-section for π−N collisions as measured by references. [22],
[23], [24], and [11], and the theoretical prediction by Berger [20] and MNR [21]. The
uncertainties shown for the measured values are the statistical and systematic contributions
added in quadrature.
13
1.1.2 Fragmentation of b quarks
After production of QQ pairs, fragmentation, or hadronization, occurs subsequently.
During this process the color forces organize the QQ pairs with other quarks created in this
process into colorless hadrons. Fragmentation is governed by soft, non-perturbative
processes that cannot be calculated from first principles and can only be modeled. In the
LUND string-breaking model [26] for example, the color energy stored in the color field
increases as the individual QQ quarks separate; then, at some point, the color field has
enough energy to produce a qq (light quark pair) or a qqqq (light diquark pair) and the
string breaks. This effect is shown in Figure 1.3. In this model the ratio of the probability
for qqqq production to that for qq is 0.09 : 1.0, where the probability for qq production
approximately 0.3. [27]. If a b (heavy) quark combines with a single light quark, the result
is a beauty meson; if it combines with a light quark pair, the result is beauty baryon. The
Q
Q
q
q
q
q
Heavy Baryon
Heavy Antibaryon
Figure 1.3. Schematic picture of fragmentation in which breaking of the lines of the color
force between the separating heavy quarks of a QQ pair produce a light qqqq diquark pair
which combines with the heavy quarks to form a heavy baryon pair .
14
probability F(Λb) of a b quark fragmenting into a Λb or into a beauty baryon that
subsequently decays into a Λb, has been measured to be 7.2 ± 1.2 % [28].
1.1.3 b-hadr on decay
Several kinds of Feynman diagrams contribute to the non-leptonic decays of b
hadrons; examples are shown in Figure 1.4. The processes shown are called spectator
(external or internal), exchange, annihilation, and penguin (electromagnetic or hadronic)
diagrams. In spectator diagrams the b quark decays in to a c quark (shown), or u quark
(not shown) and a W − boson which, in turn, decays primarily into ud or cs (favored in
the Cabbibo-Kobayashi-Maskawa (CKM) scheme), or into e e
−ν , µ νµ
−
, or τ ντ
− . In these
decays, the lighter quarks in the b hadron act only as spectators and do not participate in the
decay. It is important to mention the difference between “external” and “internal” spectator
diagrams. In the external diagram, the colorless W − is allowed to decay into three possible
ud or cs color singlet final states. In contrast, in the internal diagram, in order to form
colorless final states only one of the three possible virtual W − decays is allowed.
Therefore, the internal diagram is suppressed by a factor of 1/ Nc with respect to the
exterior diagram, where Nc is the number of colors.
15
b
q
W
−
c
q
External Spectator
u
d W
−
b
Internal Spectator
c
s
c
W
−
b
q
Annihilation
W
−
b
q
W Exchange
W
−
b
t
s
qq
γ
Electromagnetic Penguin
W
−
b
t
s
qq
g
Hadronic Penguin
q1
q3 q3
q2
q
q
q
q
Figure 1.4. Feynman diagrams for the non-leptonic decay of a b hadron.
16
The total b-quark decay width from the spectator diagrams, Γb
totSP , has been
computed to be [29]
Γb
totSP b
bc bu
G m
V V= +[ ]
2 5
3
2 2
192
2 72 6 92
π
. . , ( 1.3)
where G is the Fermi coupling constant, mb the mass of the b quark, Vbc and Vbu are the
CKM matrix elements that represent the b c→ and b u→ quark transitions, respectively.
In the W-exchange and annihilation decays, both initial-state quarks are involved in
the weak vertex; the classic example is π µ νµ
− −→ (or π ν− −→ e e). For b-hadrons these
types of decays are helicity-suppressed. To zeroth order in QCD, the total hadronic width
for W exchange, Γb
W ex, is given in Ref. [29] to be
Γb
W ex
bq qq bq b bbq q q
G
V V f m m m M m m m→( ) = +( ) ( )1 3
2 2 2 2
1
2
3
2
1 3
1
3 8 1 3π ,
, , ( 1.4)
and that for annihilation is
Γb
annih
bq q q bq b bbq q q
G
V V f m m m M m m m→( ) = +( ) ( )2 3
2 2 2 2
2
2
3
2
2 33
8 2 3π
, , , ( 1.5)
where the Vqq ′ are CKM matrix elements,
M m m m
m m
m m m
m m
m
m m
m
b
b b b
1 3
1
2
3
2 2
2
1
2
3
2
1 3
2
1 3
2
1
2
1 1 1, ,( ) = −
−( )
+( )
−
+
−
−
,
17
and fbq , called the decay constant, has dimensions of mass and is related to the amplitude
of the bq wave function at the origin by f Mbq bq
2 212 0= ( )ψ / (where Mbq is the mass of
the bq system. The value of ψ 0 2( ) can be calculated in a similar fashion as for the
hydrogen atom. It involves the reduced mass of the system, m m m m mb q b q q/ +( ) ≈ , and
the coupling constant αs; that is, ψ α0
2 3 3( ) ∝ s qm . Thus, by taking M mbq b≈ there
follows
Γ
Γ
b
W ex annih
b
total SP s
q
b
m
m
+
∝
α3
5
. ( 1.6)
Since widths are proportional to rates, this indicates that the ratio of the (W exchange +
Annihilation) decay rate to the total spectator decay rate is, in general small, since mb >>
mq.
The decay width for the penguin diagram is given by [29]
Γb
Pen
tb ts bq bbq sq c c
G
V V f m→( ) = +( )1
3
3
8
5 6
2
2
2 2 2 3
π
, ( 1.7)
where c5 and c6 are constants with values of 0.02 and -0.04, respectively, defined in Ref.
[29]. The penguin contribution to b-hadron decay is negligible (a few per cent) with
respect to the spectator contribution.
18
In the spectator-type decay where b ccs→ , the cc can bind to form a ηc , J/ψ, χ1,
′ψ , or a higher-mass charmonium state. The relative ratios for the production of some of
these states is predicted in Ref. [30] to be 0.57 : 1.0 : 0.27 : 0.31 for ηc :J/ψ: χ1: ′ψ .
The Λb → J/ψ Λ
0
decay has no nonspectator contributions; thus, the theoretical
computation of the branching ratio for this decay is relatively clean. The theoretical
prediction is that the Br(Λb → J/ψ Λ
0
) is less than 10
-3
[31].
1.2 Evidence for the existence of the Λb
While b-flavored baryons have long been predicted by the quark model, only very
recently (1992) has their existence been confirmed. Evidence for Λb baryons was
reported by LEP experiments ALEPH, DELPHI, and OPAL [10] through observation of
the semi-leptonic decay channels Λb → Λ
0 l Xl
− ν and Λb → Λc ll X
+ − ν in Z bb0 →
events. The analysis was based on correlations between the baryon and lepton produced in
the decays, since b baryons are expected to produce Λ0 l−, Λ0l+ or Λc l
+ − , Λc l
− +pairs,
and not Λ0 l+, Λ0l− or Λc l
− − , Λc l
+ + pairs (see Figure 1.5). The experiments found an
excess of events of the correct baryon-lepton combination pairs, and interpreted this excess
as Λb decays. The results, in the form of the product of production fraction and branching
ratio are, summarized in Table V.
19
1.3 Previous sear ches for the Λb → J/ψ Λ
0 decay channel
The quark diagram for the Λb → J/ψ Λ
0
decay channel is shown in Figure 1.6.
This diagram is an internal spectator diagram. Thus, it is colored-suppressed, since the cc
pair form a color-singlet state in order to be bound. Only CERN experiment UA1 has
observed Λb s in the J/ψ Λ
0 decay mode. They found a signal of 16 ± 5 events above a
Λb
b
u
d
c
u
d
s
u
d
W-
W+
Λ0
l-
νl
X
Figure 1.5. The Λb → Λ
0 l Xl
− ν decay channel quark diagram.
Table V. Results on Λ0-lepton and Λc
+-lepton correlations in Z
0
decays at LEP. The first
uncertainty is statistical and the second is systematic.
F Br l Xb b lΛ Λ Λ( ) ∗ →( )−0 ν
(10
-3
)
F Br l Xb b c lΛ Λ Λ( ) ∗ →( )+ −ν
(10
-2
)
ALEPH 6.1 ± 0.6 ± 1.0 1.51 ± 0.29 ± 0.23
DELPHI 3.0 ± 0.6 ± 0.4 1.18 ± 0.26 −
+
0 21
0 31
.
.
OPAL 2.91 ± 0.23 ± 0.25 0.83 ± 0.28
20
background of 9 ± 1 events [7], and measured the mass of the Λb to be (5640 ± 50 (stat) ±
30 (sys)) MeV/c
2
and F(Λb) * Br(Λb → J/ψ Λ
0
) to be (1.8 ± 0.6 (stat) ± 0.9 (sys))x 10-3.
ALEPH, OPAL, and CDF have failed to confirm UA1's signal (see Refs. [8] and [9]).
The results found in their search are summarized in Table Table VI.
cb
d
d
u
u s
W-Λb
Λ0
J/ψ
c
Figure 1.6. The Λb → J/ψ Λ
0
decay channel quark diagram.
Table VI. Results from other searches for the Λb → J/ψ Λ
0
decay channel.
Experiment
UA1
CDF
ALEPH
OPAL
F(Λb )∗ Br(Λb → J / ψ Λ
0 )
(1.8 ± 0.6(stat) ± 0.9 (sys)) x 10-3
< 0.4 x 10-3
< 3.4 x 10-4
< 0.5 x 10-3
21
1.4 Analysis objective
The object of this thesis is to search for the Λb beauty baryons in the Λb → J/ψ Λ
0
channel (and the charge conjugate reaction) using the 1990 data from fix-target experiment
E672 at Fermilab. The J/ψ s are identified by their decay into µ+ µ− and the Λ0 through
the decay channel Λ0 → p π−. By relating the number of Λb → J/ψ Λ
0
events to the E672
measurement of the b-quark cross-section obtained from the same data, the production rate
F(Λb) * Br(Λb → J/ψ Λ
0
) will be extracted. (Throughout this thesis, whenever a state is
mentioned its charge conjugate state is also implicitly implied.)
22
CHAPTER 2
2. THE MWEST SPECTROMETER
The MWEST spectrometer, was located at the meson-west area at Fermilab. It was
used simultaneously by experiments E672 and E706. The experiments accumulated data in
1990 and 1991. The output signals from all detector systems were available to both
experiments. E672 concentrated on dimuon events, whereas E706 was interested in events
that contained direct photons [32]. Experiment E672 was designed to study the
hadroproduction of high-mass muon pairs which resulted from heavy-quark production,
particularly charmonium [33]. This chapter begins with an overview of the complete
spectrometer and then presents a detailed description of the individual components of the
apparatus that were used to obtained the data for the analysis in this thesis.
2.1 Overview of the detector
The physical layout of the combined E672/E706 apparatus is shown in Figure 2.1.
A right-handed orthogonal coordinate system was associated with the spectrometer, with its
origin near the target and with the z-axis aligned with the beam direction. The x and y axes
were in the horizontal and vertical directions, respectively. The apparatus began with a
23
hadron shield used to absorb beam halo and a set of scintillation-counter veto walls used to
veto events with halo particles at the pretrigger level. Downstream was a Cu and Be target,
a tracking system composed of a set of 16 silicon-strip detectors (SSDs), a dipole magnet
with average p
T
kick of 0.4457 GeV/c, 16 proportional-wire-chambers (PWCs), and 4
straw drift-tube detector planes. Following this was a liquid-argon electromagnetic
(EMLAC) and hadronic (HADLAC) calorimeter, and a forward calorimeter for energy
measurement of forward-going electrons, photons, and hadrons. Finally, about 20 meters
downstream of the target was the muon spectrometer consisting of a concrete hadron shield
(beam dump) to prevent hadrons produced in the underlying event into the muon system, a
toroid magnet with average p
T
kick of 1.3 GeV/c, 12 muon PWCs, and two scintillator-
hodoscope planes (muon hodoscopes H1 and H2) with associated electronics for
generating a trigger signal upon the detection of two muons. Each of the elements pertinent
to the analysis in this thesis are discussed in more detail.
Hadron
Shield
X
Y Z
beam
Target/
SSDs
PWCs
Dipole
Magnet
Forward
Calorimeter
LAC
Muon PWCs
Toroid
Magnet
Beam
DumpStraw
Tubes
0 m 10 m 20 m Z
Veto Walls
µA, µB µ1-µ4
Muon Hodoscopes
H1 and H2
Neutron
Absorber
Beam
Hodoscope
30 m
Figure 2.1. The physical layout of the MWEST spectrometer.
24
2.2 Beam
The Fermilab Tevatron operated on a 57.2 second cycle. During which, 23
seconds were used for the spill of the beam to the experimental areas. The Tevatron
provided an 800 GeV/c proton beam to the switchyard, the area where the beam was split
and directed to the three major beam areas: meson, proton, and neutrino. The beam had a
19.7 ns bucket structure from the characteristic radio frequency of the Tevatron.
2.2.1 Beamline
The beam used in the experiment was produced in the following way: The portion
of the beam sent to the meson west area, which had a typical intensity of about 2 x 1012
protons per spill, collided with a beryllium target of dimensions, 46.5 cm in length and
2.22 cm in diameter, corresponding to 1.14 interaction lengths. This produced a secondary
π − beam of 515 ± 3 GeV/c average momentum [34], and intensity at its maximum of
2x108 π − per spill [35]. The same bucket structure applied to the secondary beam, where
the probability of a bucket being occupied by a single particle was about 10%, and the
probability of being occupied by more than one particle was approximately 2%.
Both pion and proton beams were delivered to the meson-west area through the
Fermilab meson-west beamline, which was built specifically for the experiment. This
above ground beamline was designed to transport positively and negatively charged
particles with a momentum of up to 1 TeV/c.
25
2.2.2 Cerenkov counter
The secondary beam used by the experiment in 1990 was not a pure pion beam,
97.0% of the beam particles were π − s, 2.9% K − s, and 0.1% antiprotons [35]. A
Cerenkov detector was used to tag the beam particles. The detector had dimensions of
42.1 m long and radius of 24.4 cm, and it was positioned in the direction of the beam.
Helium gas, at pressure between 4 - 8 psi, was used as the radiator. For a more detailed
explanation of the Cerenkov counters see reference [35].
2.3 Hadron shield and veto walls
A large stack of iron, of dimensions 4.7 m long, 4.3 m wide, and 3.7 m high, with
a hole in its center (for the beam particles to pass through), was placed at the end of the
beamline, just inside the experimental hall. This served as a hadron shield to absorb the
beam halo, those particles traveling in the beam direction, but not on the beam axis. Also
"spoiler" magnets in the upstream beamline were employed to sweep halo particles away
from the beam.
Halo muons, produced primarily from π − decays from the beam, could however,
pass through the iron shield very easily, and subsequently throughout the entire
spectrometer. To tag the muons so that they would not start the dimuon trigger (for
example, one muon from the target and a halo muon), a series of three "veto walls"
scintillation counters were used. One was placed just upstream of the hadron shield (VW3)
and the other two just down stream (VW1 and VW2), see Figure 2.1. The veto wall VW3
consisted of 18 rectangular scintillator counters, and it covered an area of about 3 m x 3 m.
26
Veto walls VW1 and VW2 each consisted of matrix of thirty two 50 cm x 50 cm scintillator
counters, also covering an area of approximately 3 m x 3 m. These two walls had a 10 cm
offset in the x-y plane to cover the gaps from one another. The three walls had a hole in the
central region to allow the beam to pass without generating a signal. A coincidence
(VW1+VW2) * VW3 between the walls was established to veto events containing halo
muons, and this was done at the pretrigger level.
2.4 Target
The experiment used a target composed of two pieces of Cu and two pieces of Be,
as shown in Figure 2.2. The two Cu targets were 0.8 mm thick, and were separated by a
0.26 cm air-gap. Downstream of this, 0.55 cm, was the first piece of Be, which had a
thickness of 3.71 cm, and was followed by a 1.02 cm air-gap. Finally, there was the
second piece of Be, which was 1.12 cm thick.
2.5 Upstream tracking system
This tracking system, located near the target, was used to reconstruct the tracks
(trajectories), and the vertices made by the tracks of the outgoing charged particles accepted
by the spectrometer. It had four major parts: the SSDs, the upstream PWCs, the dipole
magnet, and the STRAWS. The STRAWS will not be discussed here, since they were not
used for this analysis.
27
2.5.1 Silicon-strip detector system
The arrangement of the SSD system is shown in Figure 2.2. It consisted of 16
separate planes, 6 of them upstream of the target and 10 planes downstream. The SSD
+13 cm
+8 cm
+2 cm
-3 cm
-6 cm
-20 cm
-34 cm
-130 cm
5 cm x 5 cm wafers
50µm pitch
5 cm x 5 cm wafers
25/50µm pitch
1.12 cm Be
3.71 cm Be
0.8 cm Cu
3 cm x 3 cm wafers
50µm pitch
Be
am
Figure 2.2. The physical layout of the target and SSD system.
28
planes measured the position of a charged particle by putting out a signal induced by the
particle on the strips etched onto the silicon wafers. The 16 planes were setup in pairs,
consisting of one plane with its silicon-strips oriented in the x-direction (horizontal) and the
other in the y-direction (vertical). The 3 x-y planes upstream of the target, had an area of 3
cm x 3 cm, and a pitch of 50 µm. The 5 pairs of planes downstream of the target all had a
5 cm x 5 cm area, and except for the plane just after the target, which had a pitch of 25 µm,
they all had a 50 µm pitch.
The vertex position resolution of the SSD system was of 10 µm in the x- and y-
direction, and 350 mm in the z-direction. The angular resolution was 0.1 milliradians.
This tracking device played an important role in the reconstruction of secondary vertices,
those produced from decays in flight of particles emerging from the primary interaction.
2.5.2 Dipole magnet
A conventional liquid helium dipole magnet was used to measure the momentum of
the charged particles. This was done by measuring the deflection of their trajectory as they
passed through the magnet. The dipole magnet was operated at a current of 1050 A, giving
rise to an approximately uniform magnetic field of magnitude 0.6115 Tesla. The magnetic
field was oriented in the negative y-direction, and it extended through 2.416 m (length of
the magnetic field). A mirror plate was placed in the front (upstream side) and back of the
magnet to reduce the fringe field. Each plate had a rectangular opening to allow particles to
pass through, the one in front was 35.56 cm wide x 25.4 cm high, and the one in the back
127.0 cm x 91.44 cm. A polyethylene bag filled with helium gas was installed in the
29
central region of the magnet to reduce the multiple scattering of the practices when
traversing through the magnet.
Since the direction of the magnetic field was aligned with the y-direction (vertical),
the trajectories of the charged particles were only deflected in the horizontal x-view (x-z
plane). The effective change, in the x-component of the particle’s momentum was by the
so called " pT kick" of the magnet,
p B LT kick = 0 3 0. , ( 2.1)
where B0, the magnitude of the field, is in Tesla, and L, the length of the field, is in
meters. This was equal to 0.4457 GeV/c in the x-direction.
2.5.3 Upstream proportional wire chambers
Downstream of the dipole were a set of 16 proportional wire chambers (PWCs).
They were grouped into four modules, named: PWC1, PWC2, PWC3, and PWC4. Each
module contained a plane with its anode wires aligned with the x- (horizontal), y- (vertical),
u- (rotated +370 from the vertical), and v- (rotated - 530 from the vertical) directions. The
physical dimensions of the four modules were different in order to obtain a constant
angular acceptance. PWC1 was 1.63 m wide x 1.22 m high, PWC2 and PWC3 were 2.03
m
2
, and PWC4 was 2.44 m
2
. The anode signal planes were made of gold-plated 0.8 mm
in diameter wires, spaced at 2.54 mm. For each anode plane there were two cathode
planes, one on each side, separated by a distance of 5.74 mm. These cathode planes were
30
made of graphite-coated 1.0 mm thick mylar sheets. The chambers were filled with a gas
mixture of 18% isobutane, 2.2% isopropyl alcohol, 0.1% freon, and 79.7% argon. The
PWC system is described in grater detail in [36]
2.6 Muon system
The muon system was located at the down stream end of the spectrometer about 20
meters from the target. The physical layout of the muon detector is shown in Figure 2.3.
It consisted of: 8 upstream muon PWCs, a beam dump (made of steel and tungsten), a
conventional toroid magnet, four downstream muon PWCs, two 16-segment scintillating
counter hodoscopes, and concrete walls to shield the muon PWCs.
2.6.1 Upstream muon proportional wire chambers
The first two muon PWCs named µA and µB were installed to reduce the number
of triggers caused by the halo muons and to improve the linking tracks between the
upstream tracking system and the muon system. Both µA and µB consisted of four anode
signals planes: x, y, u, and v. The x and y planes were oriented in the horizontal and
vertical directions, respectively. The u planes were rotated 100 from the vertical, and the v
planes were rotated -100 from the vertical. The anode planes were made of 1.0 millimeter
diameter gold-plated wires, separated 3.05 mm. The dimensions of the active areas and
the numbers of wires for each anode plane are listed in Table VII.
31
20 m
30 m
D
ist
an
ce
fr
om
th
e t
ar
ge
t
25 m
µB
µ2
µ1
µ4
µ3
Toroid: average
p
T
kick 1.3 GeV/c
Beam Dump
Muon hodoscopes H1 and H2:
16-segment scintillator-
hodoscope planes
Downstream muon PWCs:
Vertical anode plane with
effective pitch of 1.2cm and the
cathode planes at ± 450 with
1.05 cm pitch
µA
Upstream muon PWCs: Each with 4 anode planes,
horizontal, vertical and ±100 from vertical of 0.3 cm pitch
Figure 2.3. The physical layout of the muon spectrometer
32
The cathode planes consisted of 1650 3.5 mil diameter Cu/Be wires, separated 1.02 mm.
The distance between adjacent cathode and anode planes was 0.95 cm. Two ground
planes were also included in each PWC module, one in front of the first cathode plane and
the other after the last cathode plane. The ground planes were made of 1725 3.5 mil
diameter Cu/Be wires, separated 1.02 mm [37]. The gas mixture used in the PWCs was
76 % argon, 15 % isobutane, 8.9 % methylal, and 0.1 % freon. For more information on
these PWCs see reference [37].
2.6.2 Toroid
An iron polarized toroid magnet was used to provide a second measure of the
momentum of the muons. The toroid was 2.44 m long, had an outer radius of 1.35 m, an
inner radius of 16.8 cm at the upstream end, and an inner radius of 19.7 cm at the
Table VII. Upstream muon PWC specifications.
PWC plane
Orientation from
the vertical Number of wires
Active area
(m2)
µA x 900 256 1.7 x 0.8
µA v -100 352 1.7 x 1.1
µB v -100 448 1.7 x 1.3
µB u 100 448 1.7 x 1.3
µB x 900 544 1.7 x 1.7
µB y 00 544 1.7 x 1.7
µA u 100 352 1.7 x 1.1
µA y 00 560 1.7 x 1.7
33
downstream end. The magnetic field created by the toroid (operated normally at 1700
amperes) was in the azimuthal direction. It had a magnitude of 2.24 T at the inner radius
and 1.74 at the outer radius. The field had no measurable dependence in the azimuthal
angle. Muons received a momentum kick in the radial direction which decreases linearly
from 1.64 GeV/c at the inner radius, to 1.27 GeV/c at the outer radius. The measurement
of the momentum of the muons was used at the trigger level and was later compared to
momentum measurement of the upstream tracking system.
2.6.3 Muon pr etrigger hodoscopes
Two scintillating hodoscopes were used in the muon spectrometer, arranged as
shown in Figure 2.3. The muon hodoscopes both had a radius of 1.5 m to match the active
area of the downstream muon PWCs. They consisted of 16 triangular scintillator segments
ordered in a circular petal pattern, as shown in Figure 2.4. Each of the segments was made
of PS-10 plastic scintillator encased in aluminum sheets. The scintillating light produced
upon the passage of a muon through a scintillator segment was collected by a BBQ doped
waveshifting bar and re-emitted at a wavelength of 410 nm. This light was collected by
RCA 8575 photomultiplier tubes operating at 2100 volts. At this voltage the hodoscopes
were at least 90 % efficient. The daisy counters were used at the pretrigger level to tag the
muons produced in the underlying event .
34
2.6.4 Downstr eam muon pr oportional wir e chambers
The main components of the muon system were the four downstream PWCs,
named: µ1, µ2, µ3, and µ4. These chambers detected the trajectories of the muons as they
passed throughout the muon system. Their arrangement is shown in Figure 2.3. The
physical dimensions of PWC µ1 are shown in Figure 2.5 (a), and the specifications of all
the downstream muon PWCs are listed in Table VIII. Each chamber contained two
cathode and one anode signal planes (see Figure 2.5(b)). The cathode planes were made
of copper clad G-10 epoxy-fiberglass sheets of 1.6 mm thickness, etched to give a pattern
of parallel strips 9.5 mm wide and separated 1 mm. The strips were oriented in the u-
16-plastic scintillator
segments
Waveshifters
Photomultipliers
Figure 2.4. The schematic view of the muon pretrigger hodoscopes
35
(+ 450 from the vertical) and v- (- 450 from the vertical) directions (see Figure 2.5(c)). The
anode planes were oriented in the y-direction (vertical) and made of 25 µm diameter gold-
plated tungsten wires, separated by 6 mm, except for µ2 which had 4 mm pitch. The
anode wires of µ1, µ3, and µ4 were connected in groups of three adjacent wires to each
amplifier card, and in pairs for µ2, so the effective pitch of each PWC was 1.2 cm. The
detail explanation of the muon PWC readout, and in general the data acquisition system
(DA), is explained in the next chapter.
Table VIII. Downstream muon PWC specifications.
Inner radius
Outer radius
Effective pitch
Anode-Cathode separation
µ1 15 cm
µ4 20 cm
µ3 18 cm
µ2 15 cm
u,v 10.5 mm
all 1.35 m
y 12.0 mm
all 9.5 mm
36
2.
8
m
9.
5
m
m
1
m
m
2.8 m
.15 m
1.35 m
Cathode planes
Anode wires
6 mm
Support plane
Support plane
Honeycomb
Honeycomb
Cathode plane
Cathode plane
Anode wiresSpacer frames
0.2 m
a)
b)
c)
Figure 2.5. Downstream muon proportional wire chamber: (a) physical dimensions; (b)
cross section of the chamber; (c) cutaway view of the chamber.
37
CHAPTER 3
3. D ATA ACQUISITION SYSTEM
The data acquisition system of the MWEST spectrometer recorded the events of
interest for both experiments, E672 and E706. E672 triggered on events that contained at
least one high-mass dimuon, and E706 had several LAC based triggers [38]. This chapter
describes the data acquisition system of the whole detector, however, only the muons
system readout is described in detail.
3.1 Overview of the data acquisition system
The data acquisition system (DA) was divided into four parts, three CAMAC based
PDP-11 systems and one FASTBUS system. A schematic diagram of the DA is shown in
Figure 3.1. The muon system was readout using a PDP-11/34, named MU. It
communicated with the muon system CAMAC interface through a Jorway 411, which read
the CAMAC crates on a serial CAMAC highway. The upstream PWCs, SSDs, and
CERENKOV counters were readout through a PDP-11/34, named NEU, and the forward
calorimeter (FCAL) through a PDP-11/34, named ROCH. The FASTBUS system was
used to readout the LAC and straw drift-tubes planes (STRAWS). The PDP-11s and
38
FASTBUS were connected to a device developed by Fermilab, called a Bison Box [39],
which controlled the beginning and ending of the spill interrupts, as well as the event
interrupts (triggers). The PDP-11s were also connected to a DEC Micro VAX II computer,
using communication device (CD) links [40]. The Micro VAX was running the
VAXONLINE software system [41], which concatenated the readout data of the PDP-11s.
This data, along with the FASTBUS data, constituted a complete event. THE VAXOLINE
also controlled the beginning and ending of the data taking process, kept a dynamical event
pool on the Micro VAX, for on-line data monitoring, and wrote the collected data to 8 mm
exabyte tapes
3.2 Muon system readout
The electronic readout of the muon system consisted of several CAMAC crates
modules which included a LeCroy PCOS III DataBus Interface (LeCroy 4299). This
collected data from the muon chambers, ADCs, TDCs, scalars, the dimuon trigger
processor (DTP), and sent it to the PDP-11 MU (see Figure 3.1).
3.2.1 Muon pretrigger hodoscope readout
The output signals from the 16 phototubes of each hodoscope were sent through a
RG58-C coaxial cable to two 16-channel CAMAC multiplicity logic units [42]. The two
modules discriminated the received signals and set a latch for each channel that exceeded a
certain preset voltage threshold during an external set gate. The multiplicity of the tracks in
the muon hodoscopes was then calculated from the multiplicity of the latch bits. The
CAMAC module could be preset to a certain multiplicity threshold, so if the calculated
39
multiplicity was grater than or equal to the set threshold, a NIM level was output. During
normal data taking the multiplicity threshold was set to two for both muon hodoscopes.
CAMAC
Databus interface
CAMAC
PCOS III
Muon chamber readout
CAMAC
ADCs, TDCs,
Scalers, Clock
CAMAC
Dimuon trigger
processor (DTP)
µ VAX II
VAXONLINE
Magnetic
tape
Online
monitoring
FASTBUS
PDP-11/34
ROCH
PDP-11/34
NEU
PDP-11/34
MU
JORWAY-411
LAC, STRAW
Readout
FCAL
Readout
PWC, SSD, CERENKOV
Readout
BISON BOX
E706
Triggers
E672
Trigger
Figure 3.1. Diagram of the MWEST detector data acquisition system.
40
3.2.2 Upstream muon proportional wire chamber readout
All the muon chambers were readout using a LeCroy PCOS III system
(Proportional Chamber Operating System) [43]. The readout signals were sent to LeCroy
2731 latch modules, which resided in CAMAC crates. Each crate could hold 23 latch
modules, and one controller (LeCroy 2738). The controller module, which queried each
latch module, stored the addresses of the active channels in an internal buffer, then sent
them to the data acquisition system. The controller also had an ECL port which transferred
data ( at a rate of 10 times that of CAMAC) to the trigger logic circuit.
3.2.3 Dimuon trigger processor
The dimuon trigger processor (DTP) was used to do an on-line calculation of the
dimuon invariant-mass. It consisted of 7 CAMAC double-width modules. These received
the data output of the muon PWCs PCOS III. The data was sent by the LeCroy 2738 crate
controller through the fast ECL port. A flow chart diagram of the DTP is shown in Figure
3.2. The wire-hit data information from the chambers, µ1 and µ4, was sent to two
modules named POINT. These modules computed in parallel (using the wire hits) the
space points of the trajectories of the muon tracks. The location of these spatial points was
checked against a look-up table stored in Programmable Read Only Memory (PROM) to
assure that the points were in the feducial volume of the muon spectrometer. The list of
valid points was stored in a Random Access Memory (RAM) and sent to two other
modules named TRACK.
41
The TRACK modules also received the wire hit information from the µ2 and µ3
muon PWCs. Using this additional information and the valid space points, they calculated
in parallel the possible associated tracks in the x (x-z plane) and y (y-z plane) views. This
list of tracks was sent to two other modules named MOMENTUM and TARGET. The
TARGET module, which also received the hit information from the upstream muon
chambers µA, and µB, checked to see if the tracks were consistent with the hits found in
the µA and µB. This was done in the following way : An imaginary straight line was
constructed from the center of the target to the point in space were the track in question met
the center of the toroid; the imaginary line was compared with the wire-hits of µA and µB,
and if the hits on at least 3 out of 4 planes in each chamber were consistent with the
imaginary line, the associated track was said to be a valid track. Again, in parallel with the
TRACK module, the MOMENTUM module calculated the momenta of the tracks from
their bend in the toroid assuming they originated from the target. The last step of the DTP
was to compute the invariant-mass of every pair-combination of valid tracks. This was
done (assuming the tracks were from muons) by a module named MASS, which received
the list of valid tracks and their associated momenta . If at least one pair-combination of
valid tracks gave an invariant-mass greater than a preset threshold, a success signal was
output. In the 1990 run, the mass threshold was usually set between 0.5 GeV/c
2
and 1.0
GeV/c
2
.
42
3.3 Dimuon trigger
The E672 dimuon trigger was activated after the detection of both a beam particle
and an interaction, and if the DA was not busy. It was done in two stages: Level 1, or
pretrigger; and level 2.
The pretrigger required that the hits in the muon hodoscopes be consistent with a
track multiplicity in the muon detector of least two tracks. If this was true and no particles
were detected by the vetowalls, level 2 was started. Muons produced in the target required
approximately 15 GeV to penetrate the spectrometer material and reach the muon
hodoscopes, all particles reaching them were assumed to be muons. The average hit
multiplicity was 2.3. The pretigger rate was 2 x 10
-4
per interaction. The pretigger
efficiency for two muons penetrating the system was 0.76 and remained constant over the
data taking period.
Level 2 was based on the requirement that at least one of the dimuons had invariant-
mass above a certain mass threshold. The invariant-mass calculation was done by the DTP
based on the information in the muon chambers. If at least one muon pairs satisfied the
DTP conditions the event was recorded to tape. The threshold of 0.7 GeV/c
2
resulted in a
trigger rate of 2 x 10
-5
per interaction.. The average DTP processing time was 10 µs per
pretigger, which included 5 µs to decode the muon chamber data. The combined efficiency
of the chambers and the DTP algorithm was 0.77 for dimuon events.
43
µ 1µ Βµ Α µ 4µ 3µ 2
LeCroy Proportional Chamber Operating System (PCOS III)
µ 1 µ 4
POINTPOINT
x y x y
yx
TRACKTRACK
TARGET MOMENTUM
MASS
Trigger
Figure 3.2. Schematic diagram of the dimuon trigger processor.
44
CHAPTER 4
4. EVENT SELECTION AND RECONSTRUCTION
The raw data were written onto 8 mm exabyte tapes. These contain the complete
information from every piece of apparatus in the entire spectrometer for all the different
events that where triggered (dimuon and LAC triggers). This chapter describes the data
reduction from the raw data to the data sample used in the analysis of this thesis.
4.1 Event selection
The first step towards reducing the data was to extract the dimuon triggers from the
raw data tapes. This step reduced the amount of the data to about 18 % of the complete
data sample, yielding approximately 5 million dimuon triggers (corresponding to a
luminosity of 8 pb
-1
). To further reduce the data, only information from the upstream
tracking system and the muon system were extracted. The information from the LAC and
forward calorimeter was excluded. By excluding this portion of the data, the event size
was reduced by a factor of 8. The set of events that were extracted is known as the “MNS”
sample.
45
4.1.1 Dimuon preselection
Because of inefficiencies of the veto walls, some halo muons activated the dimuon
trigger. Also, muons produced by beam interactions with the forward calorimeter could set
off the dimuon trigger. This happened often since the forward calorimeter only had a 3.2
cm diameter hole in the center. If it was not properly aligned, the beam could possibly
interact with the calorimeter and produce muons. To avoid events that might have any of
the two problems just mentioned, the MNS dimuon sample was run through a preselection
program. The program required that at least two muons with a momenta greater than 20
GeV/c each be present in the event. Both muons had to be consistent with originating from
the target region. Also, the track segments from the muon system had to be linked with an
upstream PWC track segment. These requirements reduced the MNS sample by 86 %.
The set of events that survived the requirements of the dimuon preselection program is
known as the “DIM” sample. This sample consists of about 750 thousand events. To
reduce the data even more, the events were required to have at least one opposite sign
dimuon pair with an invariant-mass greater than 2.0 GeV/c
2
. Approximately 35,000 events
survived these requirements. This set of events is called the “PSI” sample. It is the actual
data set used in the analysis of this thesis.
4.2 Event reconstruction
The event reconstruction program was written by Prof. Jack Martin [44]. The
program reconstructed the “tracks” (trajectories) of the charged particles detected by the
spectrometer. It first found the track segments detected by the SSD, upstream PWC, and
muon PWC systems. Using the track segments, it linked the tracks from the various
46
systems: The SSDs with the upstream PWCs, these are labeled SSD-PWC linked tracks;
and the upstream PWCs with the muon PWCs, these are called PWC-MUON linked
tracks. It also linked the track segments throughout the complete detector, these type of
tracks are called SSD-PWC-MUON linked tracks or fully linked tracks. Finally, with the
reconstructed tracks it searched for the location of the vertex in the event. All these steps
are described in detail below.
4.2.1 Track finding
The track finding algorithm for the muon PWC system began by searching each of
the view planes: u, v, and y, for groups of adjacent wire hits. These groups of hits were
called hit clusters. The center of each hit cluster (with its corresponding uncertainty of half
the width of the cluster) was used as a view hit. Having the list of view hits in each view,
a search for single-view tracks was performed. They were found by doing a search of all
the possible roads containing only one hit cluster per plane in at least 3 of the 4 planes. A
road was defined as a quadrangular portion of the active area of a given plane view of the
muon PWC system. It extended from the first PWC (µ1) to the last PWC (µ4). Figure
4.1 shows the first road used in the algorithm, and the subroads into which it is divided.
Roads that contained more than the allowed number of hit clusters were further subdivided
using a scheme as in Figure 4.1. The algorithm was repeated until the roads satisfied the
conditions mentioned above. The roads that did not meet the criteria were disregarded.
47
As a simple example of the track finding algorithm, consider the hit cluster pattern
found in the muon system as shown in Figure 4.2. After the first iteration, it is easy to see
that only subroad 3 has no more than one hit per plane in at least 3 out of the 4 planes. In
this case, it has hit clusters on all the planes. This road is not subdivided further since it
µ1 µ2 µ3 µ4
First road
Original road
Subroad 1
Subroad 2
Subroad 3
Subroad 4
Figure 4.1. Illustration showing the first roads used in the track algorithm and the scheme to
subdivide a road into other roads.
48
now meets the track finding criteria. All the other roads are disregarded. Of course the hit
cluster pattern found in a real event is far more complex than this simple example.
Once the final set of roads is found, a straight-line fit is performed to the hit clusters
within each road. This fit determines the slope and intercept of the tracks in each view.
After this, a three-dimensional space-track finding is performed in a similar fashion as in
the single-view track finding. Space-roads are constructed and checked to see if any
single-view tracks are consistent with belonging to the space-road. The space-roads that
contain more than one view-track are further subdivided. This is done until a set of space-
roads which only contain one single-view track per view is found. The hit clusters
belonging to each space-road are then fit to a straight line. The fit gives the parameters of
the space-track as the slopes and intercepts of the track in the x-z and y-z planes (x and y
views, respectively).
The track finding for the upstream PWC and SSD systems are essentially the same
as for the muon system. The only difference is that when fitting the hit clusters to find the
final parameters of the tracks, single wire hits are used instead of the hit clusters (one wire
hit from each cluster). The parameters of the single wire hit track combination, that give
the smallest χ
2
from the straight-line fit are kept as the parameters of the track. This is
done because the high multiplicity of the wire hits gives rise to spuriously large hit cluster
widths. No space-track finding is done for the SSD system, since it only had two plane
views.
49
µ1 µ2 µ3 µ4
Subroad 1
Subroad 2
Subroad 3
Subroad 4
muon track
Hit Clusters
Road with more than 3
plane hit clustes
Figure 4.2. Illustration of a simple example of the track finding algorithm, the arrow
shows the muon track.
50
4.2.2 Track linking
After reconstructing the track segments in each of the tracking devices, these are
linked from one device to another. The track linking fit determines the momenta of the
tracks by using the bend in the dipole magnet, or in the toroid, for the case of muon tracks.
The SSD-PWC track linking is performed in the following way: Track segments
from the SSD and upstream PWC are extrapolated to the center of the magnet in each view.
The segments from the y-view must meet one another within the error of track segments.
The segments from the x-view must meet each other within 5 mm. The linking in this case
is done in each view, separately, because the SSD system only has single-view tracks and
no space-tracks. The reason for the linking requirements to be different in each view is
because the dipole magnet only deflected the tracks in the x-view. Thus, the y-view tracks
should have approximately the same parameters as seen in the SSD and upstream PWC
systems. Figure 4.3 illustrates the SSD-PWC linking. Track segments that meet the
linking criteria are fit using the slopes and intercepts of each track segment: a, b, e, f; and c,
d, g, h (see Figure 4.3). The y-view fit is done with the constraint that the slope and
intercept of the track are the same in both the SSD and upstream PWC systems. In the x-
view, the fit outputs the momentum of the linked track (as1/P), the slope, and the intercept
of the track as seen by the SSD system in the x-view. Tracks that pass the χ2 quality cut of
the fits are said to be SSD-PWC linked tracks. PWC space-tracks can have up to three
SSD-x and three SSD-y link combinations if they pass the χ2 cut. These ambiguities are
resolved at a later stage.
51
Upstream PWCs Muon PWCs
SSDs Toroid
Dipole
SSDs
Upstream PWCs
Muon PWCs
Dipole
Toroid
y-z plane
x-z plane
x = a + bz
y = c + dz
x = e + fz
y = g + hz
x = i + jz
y = k + lz
1
p
1
p
1
p
,φx ,φy
1
p
,φx ,φy
Track must meet
within 12 cm
Segments must
meet within 5 mm
Segments must
meet within errors
Figure 4.3. SSD-PWC linking scheme.
52
The PWC-MUON track linking is done in the following way: The track segments
from the upstream PWC and muon PWC systems are extrapolated to the center of the
toroid. Track segments that meet one another with in 12 cm in both the x and y views are
considered as linked track candidates. Figure 4.3 shows the PWC-MUON linking scheme.
The linked track candidates are fitted using a standard χ2 minimization algorithm, using the
parameters of the track segments: e, f, g, h, i, j, k, and l. Also, the momentum (in the
form 1/P) and two multiple scattering angles (φx and φy) are included in the fit. Candidates
that pass a χ2 quality cut are said to be PWC-MUON linked tracks. Again, in the case of
ambiguities, up to 3 PWC-MUON linked combinations are kept for each muon track.
Matching of these tracks to the SSD-PWC linked tracks and to the vertex position are used
to resolve the ambiguities at a later stage. A global fit is done to the muon tracks. These
are linked throughout the entire detector. To do this, the SSD-PWC linked tracks are
extrapolated to the center of the toroid and matched with the muon tracks in the same
manner as the upstream PWC segments, described above. Here, the fit is performed using
all the parameters of each segment composing each track: a, b, c, d, e, f, g, h, i, j, k, and l.
Also, the momentum of the track in the dipole ( written as 1/P), the momentum in the toroid
( written as 1/P), and two multiple-scattering-angles φx and φy are included (see Figure
4.3). Once again, a χ2 minimization algorithm is used. Track combinations that pass a χ2
quality cut are called SSD-PWC-MUON linked tracks, or fully linked muon tracks.
To improve the resolution of the SSD-PWC linked tracks, the SSD segments
associated with a vertex were refitted using the vertex position as an additional pseudo-
plane hit. A χ2 fit like the one for the PWC-MUON linked tracks, is now performed on the
53
SSD-PWC tracks, yielding the momenta and the track parameters in each view at the
production vertex.
The fractional uncertainty in the momentum measurement of a fully linked (SSD-
PWC-MUON linked) muon track is:
δp
p
p= 0 0005. ;
as seen in Figure 4.4. The over all efficiency to reconstruct a fully linked muon track is
86%.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 50 100 150 200 250 300
P (GeV/c)
δP
/P
Figure 4.4. The fractional uncertainty of momentum vs. momentum for fully linked muon
tracks.
54
4.2.3 Vertex finding
The vertex finding algorithm begins by looking at the SSD x and y views for
intersections of two track segments. In each view, intersections that occur approximately at
the same position (within errors) are combined. A list of possible multi-segment
intersections is made for each view. The two lists are compared, and only intersections that
have consistent z positions (within errors) in both views are kept. This results in a three
dimensional position (x, y, z) of the vertices and a list of the tracks associated with each
one.
A fit minimizing the impact-parameter of each track connected to its vertex is
performed to improve the resolution of the measurement of the vertex position. Figure 4.5
shows the distribution of the primary vertices found in the events of the dimuon PSI
sample (descried in section 4.1.1) for those dimuon events that are tagged as J/ψs1. This
distribution clearly shows the target configuration as well as the SSD planes (see sections
2.4 and 2.5.1 for the target and SSD plane configurations). The comparison with the
actual physical size of the target indicates a resolution of approximately 3 mm in the
longitudinal direction. Figure 4.6 shows the transverse impact-parameter of the SSD-PWC
linked tracks to the primary vertex for the events in the PSI sample. This distribution
demonstrates a resolution of about 10 µm for the measurement of the vertex position in the
transverse plane (x-y plane).
1 See chapter 5 for the definition of J/ψ events.
55
Primary vertex z-coordinate
0
20
40
60
80
100
120
-16 -14 -12 -10 -8
(cm)
E
ve
nt
s/
(0
.2
5
m
m
)
Cu
Be Be
Figure 4.5. Distribution of the primary vertices found in the “PSI” sample for those
dimuon events that are tagged as J/ψ s.
56
0
250
500
750
1000
1250
1500
1750
2000
2250
0 5 10 15 20 25 30 35 40 45 50
Transverse impactparameter (µm)
E
nt
ri
es
/
0.
4
µm
Figure 4.6. Transverse impact-parameter of the SSD-PWC linked tracks with the primary
vertex, for events in the “PSI” sample.
57
4.3 Characteristics of reconstructed dimuon events
E672/E706 has studied the hadroproduction of charmoniuom by measuring the
ψ(2S), χ1, χ2, and directly produced J/ψ fractions contributing to the inclusive J/ψ
production (see Ref. [45] and [46]), and compared these values with those predicted by the
theoretical charmoniuom models: color evaporation [47] and color singlet [48]. We have
also, as mentioned previously, measured the bb cross section by using J/ψ s from
secondary vertices [11]. This measurement will be used later to extract the production rate
for Λb s, F(Λb)*Br(Λb → J/ψ Λ
0
). Another E672/E706 study, in which the author has
been directly involved is the measurement of the atomic number (A) dependence of the
production cross sections for vector mesons ρ/ω, φ, and J/ψ [49]. The results of this study
are not included in detail here in order to make this thesis coherent. The following is a brief
summary of the results of these three studies.
The invariant mass spectrum of our 1990 opposite sign muon pairs is shown in
Figure 4.7. This is our so called “DIM” sample (see 4.1.1 for the for its definition). This
sample contains approximately 36 K ρ/ω, 10 K φ, and 12 K J/ψ. A closer look at the J/ψ
region (see Figure 4.8) shows a ψ(2S) signal which contains 270 ± 35 (stat) ± 50 (sys),
ψ(2S) → µ+ µ− events. The ψ(2S) is observed in both the µ+ µ− and J/ψ π+ π− modes.
Figure 4.9 shows the J/ψ π+ π− invariant-mass spectrum. A fit to the signal yields 224 ±
44 (stat) ± 20 (sys), ψ(2S) → J/ψ π+ π− events. Differential cross sections for J/ψ and
ψ(2S) can be found in [45]. The total integrated cross sections were measured to be
Br( J/ψ → µ+ µ− ) σ(π− Be → J/ψ + X)/A = (9.3 ± 1.1(sys)) nb/nucleon for xF > 0.1, and
Br( ψ(2S) → J/ψ π+ π− ) σ(π− Be → ψ(2S) + X)/A = (7.4 ± 1.5 (stat) ± 1.2 (sys))
58
nb/nucleon for xF > 0.1. The fraction of inclusive J/ψ yield due to ψ(2S) meson decays
was found to be 0.083 ± 0.017 (stat) ± 0.013 (sys) [45].
0
1000
2000
3000
4000
5000
6000
7000
8000
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
µ+µ- mass (GeV/c2)
C
om
bi
na
ti
on
s/
1
0
M
eV
/c
2
Figure 4.7. Invariant-mass spectrum of the opposite sign muon pairs.
59
1
10
10 2
10 3
1.5 2 2.5 3 3.5 4 4.5 5 5.5
µ+µ− mass (GeV/c2)
C
om
bi
na
ti
on
s/
30
M
eV
/c
2
J/ψ
ψ(2S)
Figure 4.8. Invariant-mass spectrum of the opposite sign muon pairs in the J/ψ region.
The solid line is a fit to the data.
60
0
25
50
75
100
125
150
175
200
3.4 3.6 3.8 4 4.2 4.4
J/ψπ+π− mass (GeV/c2)
C
om
bi
na
ti
on
s/
5
M
eV
/c
2
Figure 4.9. Invariant-mass spectrum of J/ψ π+ π− combinations. The solid line is a fit to
the data.
61
χ1 and χ2 states are reconstructed via their decay into J/ψ γ. The γ s are detected
via their conversions into e
+
e
-
pairs. Figure 4.10 shows the J/ψ γ spectrum for converted
γ s. Clear peaks are seen for both χ1 and χ2. A fit to the signals yields 57 ± 13 (stat) ± 16
(sys) and 40 ± 10 (stat) ± 14 (sys) χ1 and χ2, respectively. The integrated total cross
sections associated with these values are Br( χ1 → J/ψ γ) σ(π
−
Be → χ1 + X)/A = (50.5 ±
9.0 (stat) ± 4.1 (sys)) nb/nucleon for xF > 0.1 and Br( χ2 → J/ψ γ) σ(π
−
Be → χ2 + X)/A
= ( 35.5 ± 7.8 (stat) ± 7.6 (sys)) nb/nucleon for xF > 0.1. Thus the fraction of inclusive
J/ψ yield due to χ1 and χ2meson decays are 0.24 ± 0.04 (stat) ± 0.03 (sys) and 0.017 ±
0.04 (stat) ± 0.02 (sys), respectively.
Combining the 0.083 ± 0.017 (stat) ± 0.013 (sys) of J/ψ s due to ψ(2S) and
assuming 0.02 of the inclusive J/ψ are from χ0 and b-hadron decays, the fraction of the
total inclusive J/ψ produced directly is 0.49 ± 0.05 (stat) ± 0.05 (sys) [46]. A comparison
of our measurements with the theory are shown is Figure 4.11.
62
.
0
5
10
15
20
25
30
35
40
3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4 4.1
µ+µ-γ mass (GeV/c2)
C
om
bi
na
ti
on
s/
1
0
M
eV
/c
2
Figure 4.10. Invariant-mass spectrum of J/ψ γ combinations for converted γ s. The solid
line is a fit to the data
63
0
0.2
0.4
0.6
µ=M/2 MRS D0/:p P3:π
enhanced pion-quarks
J/ψ
χ1
F
ra
n
ct
io
n
0
0.2
0.4
0.6
102 10
3
Beam Energy (GeV)
J/ψ
χ1
χ2
ψ(2S)
F
ra
n
ct
io
n
χ1
χ2
ψ(2S)
a)
b)
ψ(2S)
J/ψ
χ2
χ2
χ1
Figure 4.11. (a) A comparison of our measurements of the fraction of inclusive J/ψ yield
due to ψ(2S), χ1, χ2, and directly produced J/ψ s, to the fractions predicted by the color
evaporation model [47]; and (b) to the fractions predicted by the color singlet model [48].
64
E672 has also measured the bb cross section [11]. This analysis was performed by using
J/ψ s emerging from secondary vertices in the regions of the target where only air was
present. E672 found an excess of 8 events in the air-gap regions of the target, and
attributed these to b → J/ψ + X decays. Which correspond to an inclusive cross section of
75 ± 31 (stat) ± 26 (sys) nb/nulceon for all xF. Some exclusive B hadron events were also
reconstructed. Figure 4.12 shows the combined invariant-mass spectrum for B
±
→ J/ψ
K
±
and B
0
→ J/ψ K0* events. There are five events near the nominal mass of the B, 3 of
them are from J/ψ K± and 2 from J/ψ K0*.
In another study, we look at the atomic number dependence of the total and
differential cross sections for the vector mesons ρ/ω, φ and J/ψ and low-mass Drell-Yan
pairs in the Feynman-x region 0.1 < xF < 0.8. By parameterizing the total cross-section as
σ0 A
α
, we find the values for α to be equal 0.74 ± 0.01 (stat) ± 0.02 (sys), 0.80 ± 0.01
(stat) ± 0.02 (sys), and 0.92 ± 0.02 (stat) ± 0.02 (sys), for these vector mesons,
respectively. We find the value of α for the Drell-Yan dimuon continuum equal to 1.16 ±
0.08 (stat) ± 0.02 (sys) for dimuon masses between 4.0 GeV and 7.0 GeV. We found no
significant dependence of the α parameter on xF or the transverse momentum pT [49].
65
Figure 4.12. Combined invariant-mass spectrum for B
±
→ J/ψ K± and B0 → J/ψ K0*
(hatched).
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2
4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5
J/ψ K, J/ψ K* mass (GeV/c2)
E
ve
nt
s/
5
0
M
eV
/c
2
66
CHAPTER 5
5. THE J/ψ → µ+ µ- SAMPLE
The J/ψ → µ+ µ− event selection begins by including all dimuons from the “PSI”
data sample (the procedure to reduce the raw data to the “PSI” sample is explained in
section 4.1.1.). Each dimuon is refitted using a standard χ2 technique, and only dimuons
that survive the χ2 cut are kept, but no more than one dimuon per event. This chapter
describes the requirements for the selection of J/ψ → µ+ µ− events used in the Λb → J/ψ Λ
0
analysis of this thesis. The details of the dimuon refit are explained in Appendix A.
5.1 Selection of the J/ψ → µ+ µ - sample
The dimuon invariant-mass distribution for the “PSI” sample is shown in Figure
5.1. A fit to this distribution that included the Monte-Carlo resolution functions for the J/ψ
and ψ(2S), and two exponential functions for the background, yields a J/ψ mass of (3.097
± 0.001) GeV/c2. This value of the J/ψ mass is in agreement with the world average value
from the particle data group [12]. The J/ψ signal region is defined as the mass interval
from 2.85 GeV/c
2
to 3.35 GeV/c
2
. This region contains about 13,053 muon pairs, with a
background subtracted signal of 11,500 J/ψ events.
67
The muon tracks in the signal region are then refitted with the constraint that both
muons intersect at a common point and that the invariant-mass is equal to 3.097 GeV/c
2
.
This constrained fitting technique improves the momentum resolution as compared to initial
track finding by a factor of 2. Also, the vertex position resolution of dimuons improved by
15 %. See appendix A for plots of the momentum and vertex residuals before and after the
fit. The quality of the fit was used to reduce combinatorial background. A cut on the χ2
per degree of freedom of the fit, to be less than 5.0, reduced the µ+ µ− background in the
J/ψ signal region by 50%. A total of 12,340 muon pairs survived the refit criteria.
68
µ+µ- Mass
0
100
200
300
400
500
600
700
2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5
GeV/c2
E
ve
nt
s
/
10
M
eV
/c
2
Figure 5.1. The dimuon invariant-mass distribution for the “PSI” sample. The solid line is
a fit to the data that includes the Monte-Carlo resolution functions for the J/ψ and ψ(2S),
and two exponential functions for the background.
69
CHAPTER 6
6. THE Λ0 → p π- (AND CHARGE CONJUGATE) SAMPLE
The great majority of Λ0 s produced in this experiment decayed after the
target/SSDs. Therefore, the tracks of their daughter decay products (proton and pion) were
not detected before their trajectories were deflected by the magnetic field of the dipole
magnet. Thus, their reconstruction is more complex. The Λ0 → p π− decays can be
reconstructed if the Λ0 s decayed upstream of the PWC system, see Figure 2.1. In
particular there are three regions in the spectrometer where this reconstruction can be
achieved: near the target/SSDs, upstream of the dipole magnet, and inside the dipole
magnet, see Figure 6.1. In the region near the target/SSDs, the proton and pion are
detected by the SSD and PWC systems, but, for the other two regions they are only
detected by the PWC system. This is important, because the standard way of determining
the momentum of a charged particle is by measuring the deflection of its trajectory upon
passing through a magnetic field. This chapter describes the procedure and algorithms
used to reconstruct Λ0 → p π− decays. Also, to confirm the validity of the reconstruction
algorithms, K
0
s → π
+
π− decays (which because of their lifetime have the same topology
as Λ0 → p π− decays) are reconstructed in similar fashion, and they are also used to clean
70
the Λ0 (and Λ0 ) sample. I remind the reader that the throughout this thesis whenever a
particle or a reaction is mentioned the charge conjugate particle or reaction is implicitly
implied.
Target/
SSDs
Dipole Magnet PWC system
Region I Region II Region III
Upstream of the
dipole magnet Inside the dipole magnet
Beam
Figure 6.1. Regions in the spectrometer where Λ0 s can be reconstructed.
6.1 Reconstruction algorithms for the Λ 0
An important characteristic of Λ0 decay in the laboratory frame, is the imbalance in
momentum between the decay proton and pion. Because of the large difference in mass
between the the proton and pion, the proton from the Λ0 decay will have on the average
larger momentum than the pion1. In the Λ0 → p π− events accepted by the E672/E706
1 Mp = 0.938 GeV/c
2
, Mπ = 0.1389 GeV/c
2
and in the center-of-mass frame p
*
= 0.101
GeV/c, thus, Ep
* = 0.943 GeV and Eπ
* = 0.172 GeV. Therefore, after boosting the proton
and pion momenta to the laboratory frame, on the average, the proton will have a larger
momentum than the pion by a factor of approximately Ep
*
/ Eπ
*
(= 5.48).
71
detector, the proton always had larger momentum than the pion (this was determined by
Monte-Carlo). Thus, when performing the two-track combinations to reconstruct the Λ0,
the track with the largest momentum of the two is always assumed to be the proton.
6.1.1 Reconstruction near the target/SSDs region
The topology of the Λ0 → p π- decay in this region is illustrated in Figure 6.2. For
these decays, the tracks of the daughter particles are reconstructed using the SSD and PWC
systems. Their momenta are measured by linking the SSD tracks to their proper PWC
tracks as explained in section 4.2.2. The Λ0 s are then reconstructed by taking two SSD-
PWC linked track combinations, assigning the proton mass to the track with the largest
momentum of the two, and the pion mass to the other one. The proton and pion tracks are
required to form a vertex. This means that the distance of closest approach between the
two tracks is less than 50 µm. In order to see a clear Λ0 signal, this vertex should be at
least 1.5 cm downstream of the production vertex of the Λ0, which in this case is assumed
to be the J/ψ decay vertex. According to Monte-Carlo, an impact parameter of a track to the
primary vertex of less than 200 µm means the track is associated with the primary vertex.
r
Pp
p track
reconstructed
trajectory
Λ0
π− track
r
Pπδp
δπ
δΛ0
r
PΛ0
Λ0 decay
vertex
J/ψ decay vertex
assumed to be the
Λ0 production vertex
At least 1.5 cm
Figure 6.2. The illustration shows the topology of a Λ0 → p π− decaying near the
target/SSD region.
72
Therefore, the impact parameter of the pion δπ relative to the Λ
0 production vertex is
required to be greater than 200 µm. Since the proton has a tendency of following the
direction of its parent Λ0, it is easy for the vertex reconstruction program to assign the
proton track to the primary vertex. The cut on the impact parameter of the proton δp relative
to the Λ0 production vertex is therefore looser than that for the pion and it is required to be
greater than 100 µm. Also, according to Monte-Carlo the impact parameter δ
Λ0
of the
reconstructed Λ0 relative to its production vertex should be less than 120 µm. Using all
these criteria a clear signal for Λ0 (and Λ0) is seen in Figure 6.3. The Λ0(and Λ0) signal
region is defined as the mass interval from 1.112 GeV/c
2
to 1.118 GeV/c
2
, and there are
10 Λ0(and Λ0) candidates. A fit to this distribution that included a gaussian function, and a
second order polynomial function for the background, yields 9 ± 3 (stat) background-
subtracted events, and a Λ0(and Λ0) mass of (1.114 ± 0.0004) GeV/c2, with a FWHM
mass resolution of 2.3 MeV/c
2
. This value of the Λ0(and Λ0) mass is in agreement with the
world average value from the particle data group [12].
73
0
1
2
3
4
5
6
1.08 1.09 1.1 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18
pπ- mass (GeV/c2)
C
om
bi
na
ti
on
s/
1
M
eV
/c
2
Figure 6.3. Invariant-mass distribution using only SSD-PWC tracks for p π− (and p π+)
track combinations intercepting in the target/SSDs region. The solid line is a fit to the data.
74
6.1.2 Reconstruction in the region upstream of the dipole
magnet
Taking advantage of the two-body decay kinematics, and assuming the production
vertex of the Λ0 s to be the J/ψ decay vertex, the Λ0 s that decayed in this region can be
reconstructed. The first step is to determine the Λ0 decay vertex (x, y, z). The dipole
magnet only bent the trajectory of the electricly charged particles in the x-z plane.
Therefore, the y and z coordinates are found from the intersection of the proton and pion
PWC tracks in the y-z plane, see Figure 6.4. Knowing y and z, and assuming an x
coordinate for the Λ0 decay vertex, the corresponding momenta of the proton and pion can
be computed. This can be determined by extrapolating the PWC tracks in the x-z plane to
x-z plane
y-z plane
z
PWCs/STRAWS
target/SSD
target/SSD
Dipole magnet
Dipole magnet
(x,z)
(y,z)
197.73 cm76.93 cm
Figure 6.4. Illustration of the proton and pions PWC tracks, for those Λ0 s that decayed in
the region upstream of the dipole magnet. The solid lines are the reconstructed PWC
tracks.
75
the center of the dipole magnet, and using the Λ0 decay vertex to estimate the deflection of
their trajectories throughout the dipole magnet, see Figure 6.4. See also Appendix B for
the explicit calculation of the momentum vectors.
To find the actual x coordinate of the Λ0 decay vertex, the assumed position of the x
coordinate is scanned across the x-axis for the value such that the vector sum of the
transverse momentum of the proton and pion with respect to the direction of flight of the Λ0
divided by the sum of their magnitudes (this ratio is called the " relative pT ", see Figure
6.5) is a minimum. Real Λ0 decays should have, in principle, minimum relative pT equal to
zero; thus, cutting on this quantity removes undesired background to Λ0 decays originating
from accidental intersections of tracks. Figure 6.6 shows the distribution of minimum
relative pT for proton and pion tracks intersecting upstream of the dipole magnet.
According to Monte-Carlo studies, 99 % of reconstructed Λ0 s have minimum relative pT
less than 0.4. Thus, a cut on minimum relative pT of less than 0.4 is imposed on the data.
Λ0 production
vertex
Λ0 direction
PTπ−
PTp
PTπ−
PTπ−PTp
PTp
+
+
relative pT =
Λ0
Pp
Pπ−
δ p
δ π
Figure 6.5. The illustration shows the topology of a Λ0 → p π− decay, and the definition
of relative pT.
76
To reject more undesired background to Λ0, the proton and pion PWC tracks are
required to not be linked to any SSD track. Also, because of the small difference between
the Λ0 and proton mass, the proton tends to follow the trajectory of the parent Λ0. Thus,
minimum relpt
0
25
50
75
100
125
150
175
200
225
0 0.1 0.2 0.3 0.4 0.5 0.6
N
um
be
r
of
E
nt
ri
es
Figure 6.6. Distribution of minimum relative pT for tracks intersecting upstream of the
dipole magnet.
77
the impact parameter of the proton δp relative to the Λ
0
production vertex is required to be
less than 1.5 cm (this value was determined from Monte-Carlo). The invariant-mass
distribution for the p π− (and p π+) combinations for this region is shown in Figure 6.7. A
clear signal for Λ0(and Λ0) is seen. The Λ0 (and Λ0) signal region is defined as the mass
interval from 1.105 GeV/c
2
to 1.125 GeV/c
2
, and there are 479 candidates. A fit to this
distribution that included a gaussian function, and a fourth order polynomial function for
the background, yields 220 ± 23 (stat) background subtracted events, and a Λ0(and Λ0)
mass of (1.116 ± 0.0004) GeV/c2, with a FWHM mass resolution of 8.0 MeV/c2. This
value of the Λ0(and Λ0) mass is in agreement with the world average value from the particle
data group [12].
78
0
20
40
60
80
100
120
1.05 1.075 1.1 1.125 1.15 1.175 1.2 1.225 1.25
pπ- mass (GeV/c2)
C
om
bi
na
ti
on
s/
2
M
eV
/c
2
Figure 6.7. Invariant-mass distribution using only PWC tracks for p π− (and p π+)
combinations for tracks intercepting in the region upstream of the dipole magnet. The solid
line is a fit to the data.
79
6.1.3 Reconstruction inside the dipole magnet region
For those Λ0 s that decayed inside the dipole magnet the reconstruction algorithm is
similar as for those that decay upstream of the magnet. Again, the reconstruction algorithm
begins by finding the (y, z) coordinates of the Λ0 decay vertex. The y and z coordinates
are determined by the intersection of the proton and pion PWC tracks in the y-z plane, see
Figure 6.8. The determination of the x coordinate is the same as before. Knowing the y
and z coordinates and with a given x coordinated for the Λ0 decay vertex, the momenta of
the proton and pion are estimated by measuring the radii of their unique circular trajectories
through the dipole magnet projected onto the x-z plane. These circular trajectories are such
that they include the point (x, z). Also at the downstream end of the dipole magnet (z=
y-z plane
x-z plane
z
target/SSD
target/SSD
Dipole magnet
Dipole magnet
(y,z)
(x,z)
197.73 cm 318.53 cm
PWCs/STRAWS
Figure 6.8. Illustration of the proton and pion PWC tracks, for those Λ0 s that decayed in
the region inside the dipole magnet. The solid lines are the reconstructed PWC tracks.
80
318.53 cm) they match the slopes of the reconstructed PWC tracks (see Figure 6.8). See
also Appendix C for the detailed calculation of the momentum vectors.
To find the actual x coordinate of the Λ0 decay vertex, the assumed position of the x
coordinate is scanned across the x-axis for the value of x such that the relative pT is a
minimum (see Figure 6.5 for the defenition of relative pT). Real Λ
0
decays should have, in
minimum relpt
0
20
40
60
80
100
0 0.1 0.2 0.3 0.4 0.5 0.6
N
um
be
r
of
E
nt
ri
es
Figure 6.9. Distribution of minimum relative pT for tracks intersecting inside the dipole
magnet.
81
principle, minimum relative pT equal to zero; thus, cutting on this quantity removes
undesired background to Λ0 decays originating from accidental intersections of tracks.
Figure 6.9 shows the distribution of minimum relative pT for proton and pion tracks
intersecting inside the dipole magnet. Again, according to Monte-Carlo studies, 99 % of
reconstructed Λ0s (and Λ0s) have minimum relative pT less than 0.4. Thus, a cut on the
minimum relative pT to be less than 0.4 is imposed on the data.
To further reduce the background to Λ0, the proton and pion PWC tracks are
required to not be linked to any SSD track. The impact parameter of the proton δp relative
to the Λ0 production vertex is required to be less than 1.5 cm. The invariant-mass
distribution for the proton-pion combinations that intersect this region is shown in Figure
6.10. A clear signal for Λ0(and Λ0) is seen. The Λ0 (and Λ0) signal region is defined as
the mass interval from 1.10 GeV/c
2
to 1.13 GeV/c
2
, and there are 582 candidates. A fit to
this distribution that included a gaussian function, and a fourth order polynomial function
for the background, yields 346 ± 26 (stat) background subtracted events, and a Λ0(and Λ0)
mass of (1.115 ± 0.0006) GeV/c2 with a FWHM mass resolution of 14 MeV/c2. This
value of the Λ0 (and Λ0) mass is in agreement with the world average value from the
particle data group [12].
82
0
20
40
60
80
100
1.05 1.075 1.1 1.125 1.15 1.175 1.2 1.225 1.25 1.275
pπ- mass (GeV/c2)
C
om
bi
na
ti
on
s/
3
M
eV
/c
2
Figure 6.10. Invariant-mass distribution using only PWC tracks for p π− (and p π+)
combinations for tracks intercepting in the region inside the dipole magnet. The solid line
is a fit to the data.
83
6.2 The K0s → π
+ π- signal
Since the K
0
s meson has a lifetime of the same order of magnitude (10
-10
s) as the
Λ0, the K0s → π
+
π− decays have the same topology as the Λ0 → p π− decays. Thus, the
K
0
s → π
+
π− decay becomes a substantial background to the Λ0 → p π− decays.
However, the K
0
s will be used to cross-check the reconstruction algorithms and to clean
the Λ0 (and Λ0 ) samples. This is needed in order to avoid ambiguities when searching for
the Λb → J/ψ Λ
0
decay (and charge conjugate).
6.2.1 The K0s → π
+ π- signal in the region near the target/SSDs
For decays in this region, the two pion SSD-PWC linked tracks are required to
form a vertex (distance of closest approach < 50 µm). In order to resolve the K0s vertex
from the primary vertex the K
0
s decay vertex should be at least 0.2 cm downstream of the
J/ψ decay vertex (the assumed production point of the K0s). Again, according to Monte-
Carlo, an impact parameter of a track to the primary vertex of less than 200 µm means the
track is associated with the primary vertex. Thus, the impact parameter of each pion δπ
relative to the K
0
s production point must be greater than 200 µm. Also according to
Monte-Carlo the impact parameter of the reconstructed K
0
s relative to its production point
must be less than 120 µm. A clear signal for the K0s is observed at the nominal K
0
s mass
of 0.497 GeV/c, as seen in Figure 6.11.
84
0
5
10
15
20
25
30
35
40
0.3 0.4 0.5 0.6 0.7 0.8 0.9
π+π- mass (GeV/c2)
C
om
bi
na
ti
on
s/
6
M
eV
/c
2
Figure 6.11. Invariant-mass distribution using only SSD-PWC tracks for π+ π− track
combinations intercepting in the target/SSDs region.
85
6.2.2 The K0s → π
+ π- signal in the regions upstream and inside
the dipole magnet
In both of these regions the requirements are that the pion PWC tracks are not
linked to any SSD track, and that the minimum relative pT is less than 0.4, as in the Λ
0
case. However, unlike in the Λ0 → p π− decay where the proton tends to follow the
direction of its parent Λ0, the pions from the K0s decay have no prefered direction. Thus,
no impact parameter is imposed on the pions. To enhance the Κ0s signal its transverse
momentum is required to be greater than 0.4 GeV/c. These cuts resulted in clear signals in
both regions for the K
0
s at the nominal mass of 0.497 GeV/C. See Figure 6.12 and Figure
6.13.
86
0
50
100
150
200
250
0.3 0.4 0.5 0.6 0.7 0.8 0.9
π+π- mass (GeV/c2)
C
om
bi
na
ti
on
s/
6
M
eV
/c
2
Figure 6.12. Invariant-mass distribution using only PWC tracks for π+ π− combinations
for tracks intercepting in the region upstream of the dipole magnet.
87
0
20
40
60
80
100
120
140
0.3 0.4 0.5 0.6 0.7 0.8 0.9
π+π- mass (GeV/c2)
C
om
bi
na
ti
on
s/
6
M
eV
/c
2
Figure 6.13. Invariant-mass distribution using only PWC tracks for π+ π− combinations
for tracks intercepting in the region inside the dipole magnet.
88
6.2.3 Distinguishing the Λ0 → p π - (and charge conjugate)
decays from the K0s → π
+ π- decays
The K
0
s → π
+ π− and Λ0 → p π− (or Λ0 → p π+) decays are difficult to
distinguished them from one another without particle identification. One can, however, try
to distinguish the two decays by plotting the Podolanski-Armenteros plot [51], defined as
the plot of the magnitude of the pT of either decay daughter particle relative to the direction
of flight of the parent particle versus the asymmetry in of longitudinal momentum (in the
laboratory frame) of the daughter particles, p p p pL L L L
+ − + −−( ) +( ) . It is easy to show that
there is a kinematically allowed region bounded by:
p p
p p
E E
E E
p
E E
p
p
L L
L L T
+ −
+ −
+ −
+ −
+ −
−
+
−
−
+
+
+ =
* *
* *
*
* *
*
2
2
2
2
2
1;
where E*+ , E*− , and p
*
are the energy and momenta of the daughter particles in the
center-of-mass frame, and pTmax = p
*
. Figure 6.14 shows the Podolanski-Armenteros
boundaries for the K
0
s → π
+ π−, Λ0 → p π−, and Λ0 → p π+ decays, and Figure 6.15
shows the Podolanski-Armenteros distribution of the Λ0 (and Λ0 ) candidates decaying
upstream the dipole magnet. These include all the combinations between 1.105 GeV/c
2
and
1.125 GeV/c
2
in Figure 6.7. A cut on the pT of the decaying particles relative to the
direction of flight of the parent particle to be less then 0.18 GeV/c is imposed to reject
possible K
0
s → π
+ π− events. This value was suggested from Monte-Carlo since 100 % of
the Λ0 → p π−, and Λ0 → p π+ decays are retained. The Λ0 (and Λ0 ) candidates were
89
reduced to 10, 471, and 578 events, in the target/SSDs, upstream of the dipole magnet, and
inside the dipole magnet regions, respectively.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
pL
+ − pL
−( ) pL+ + pL−( )
P
T
(G
eV
/c
)
Ks
0
Λ0Λ0
Figure 6.14. Podolanski-Armenteros plot for the K
0
s → π
+ π−, Λ0 → p π−, and Λ0 → p
π+ decays.
90
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
(p
+
L-p
-
L)/(p
+
L+p
-
L)
p T
(
G
eV
/c
)
Figure 6.15. Podolanski-Armenteros plot for the Λ0 (and Λ0 ) candidates decaying
upstream the dipole magnet. These included all the combinations between 1.105 GeV/c
2
and 1.125 GeV/c
2
in Figure 6.7. The lines are the kinematical boundaries for the K
0
s →
π+ π−, Λ0 → p π−, and Λ0 → p π+ decays (see previous Figure).
91
However, even after applying the cut described in the previous paragraph there is
still K
0
s → π
+ π− contamination from the outer sides of the Λ0 and Λ0 boundary regions.
Figure 6.16 shows the mass spectrum of p π− and pπ+ combinations that passed the
Podolanski-Armenteros cut from the region upstream of the magnet, when both tracks are
assigned pion masses. The solid line is the expected distribution obtained from Monte-
Carlo, normalized to have the same number of events as the data in the in the mass interval
between 0.3 GeV/c
2
and 0.45 GeV/c
2
. A similar plot is shown in Figure 6.17 for those
events in the region inside the magnet.
There is a clear K
0
s → π
+ π− contamination. Because of this K0s → π
+ π−
background, any Λ0 (or Λ0 ) candidate that has an invariant-mass consistent with that of the
K
0
s under the assumption of both tracks being pions, is excluded from the Λ
0
(and Λ0 )
sample. The K
0
s mass range in each of the regions is: (0.48 - 0.51) GeV/c
2
, (0.475 -
0.525) GeV/c
2
, and (0.45 - 0.55 GeV/c
2
), for the target/SSD, upstream of the magnet, and
inside the magnet, respectively. This cut retained 90% (9 combinations), 67% (318
combinations), and 49% (285 combinations), in each region respectively. The efficiency
of this cut according to Monte-Carlo is 90%, 67%, and 49%, for each region, respectively.
92
0
10
20
30
40
50
60
0.3 0.4 0.5 0.6 0.7 0.8 0.9
π+π- mass (GeV/c2)
C
om
bi
na
ti
on
s/
1
0
M
eV
/c
2
Figure 6.16. Invariant-mass spectrum of p π− and pπ+ combinations that passed the
criteria of being a Λ0 decaying in the region upstream of dipole magnet when both tracks
are assigned pion masses. The solid line is the expected distribution obtained from Monte-
Carlo and the dots are from data.
93
0
10
20
30
40
50
60
70
80
0.3 0.4 0.5 0.6 0.7 0.8 0.9
π+π- mass (GeV/c2)
C
om
bi
na
ti
on
s/
2
0
M
eV
/c
2
Figure 6.17. Invariant-mass spectrum of p π− and pπ+ combinations that passed the
criteria of being a Λ0 decaying in the region inside of dipole magnet when both tracks are
assigned pion masses. The solid line is the expected distribution obtained from Monte-
Carlo and the dots are from data.
94
CHAPTER 7
7. THE Λb→ J/ψ Λ
0 DECAY CHANNEL
This chapter includes a description of the Λb→ J/ψ Λ
0
Monte-Carlo simulation, as
well as the search method and the results from the search for Λb→ J/ψ Λ
0
events in our
experiment.
7.1 The Λb→ J/ψ Λ
0 Monte-Carlo simulation
A Monte-Carlo simulation of Λb→ J/ψ Λ
0
events was used to tune the
reconstruction program to search for such events in our data. It was also used to measure
the acceptance of our detector and the efficiency of the reconstruction program for this type
of events. The Monte-Carlo was a GEANT3-based full detector simulation [52].
The Monte-Carlo simulation generates a bb pair according to the next-to-leading
order (NLO) calculations of Mango, Nason, and Rodolfi (MNR), and it includes the
following parameters: the mass factorization scale Q = mb/2, the ΛQCD = Λ5 = 204 MeV,
and the MRS235 and SMRS parton distribution fuctions for the nucleon and pion,
respectively [21]. The two-dimensional distribution of xF vs. pT
2 for the generated b
95
quarks is shown in Figure 7.1, and the projections on xF and pT
2 are shown in Figure 7.2.
The Λb s are assumed to have the same momentum as their parent b quarks. They are
assigned a mean lifetime of 1.07 10
-12
s, and a mass of 5.641 GeV/c
2
. Both of these
values are taken from the PDG book [12]. In each event, one of the Λb s in chosen at
random and forced to decay into J/ψ Λ0, with J/ψ → µ+µ− and Λ0 → p π−, or the charge
conjugate reactions in the case of a Λb . It is assumed that the Λb s are unpolaraized and
that their decay is isotropic in the center-of-mass frame. The other b hadron was forced to
decay into a kaon plus a randomly chosen number of pions ( up to a maximum of 5). With
the remainder of the energy, hadrons in the underlying event are generated subject to
energy, momentum and charge conservation, according to a longitudinal phase space. See
reference [53] for a detailed description of the model.
96
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
2
4
6
8
10
12
14
16
0
200
400
600
800
1000
1200
x
F
pT
2 ((Ge
V/c)
2 )
N
um
be
r
of
E
nt
ri
es
Figure 7.1. Generated xF vs. pT
2 distribution of the b quark from Monte-Carlo events.
97
0
1000
2000
3000
4000
5000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
xF
N
um
. o
f
E
nt
./
B
in
a)
0
1000
2000
3000
4000
5000
6000
0 2 4 6 8 10 12 14 16
pT
2
((GeV/c)
2
)
N
um
. o
f
E
nt
./
0
.8
(
G
eV
/c
)2
b)
Figure 7.2. (a) Generated xF distribution of the b quark from Monte-Carlo events
(projection from the two-dimesional distribution); and (b) generated pT
2 distribution of the
b quark from Monte-Carlo events (projection from the two-dimesional distribution).
98
All the events in the generated file were run through the detector geometry by
GEANT. The resultant two-dimensional dimuon acceptance as a function of xF and pT
2
from Λb→ J/ψ Λ
0
events is shown in Figure 7.3. Our detector only accepted dimuons in
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0
2
4
6
8
10
12
14
16
0
0.1
0.2
0.3
0.4
0.5
0.6
x
F
pT
2 ((Ge
V/c)
2 )
A
cc
ep
ta
nc
e
Figure 7.3. Two-dimensional dimuon acceptance as a function of xF and pT
2 from Λb→
J/ψ Λ0 events.
99
the xF> 0 region. The integrated acceptance for these J/ψ s is 0.18 in the region xF > 0.
The events that had a dimuon accepted by the apparatus were digitized as
spectrometer hits with appropriate detector noise and efficiency to produce a fake raw-data
file. This file was then run through the same reconstruction and analysis program as that
used for the data. Figure 7.4 shows a comparison of the track multiplicity in the Monte-
Carlo with that in the data. Figure 7.5 and Figure 7.6 compare the momenta and pT of
hadron tracks from Monte-Carlo and data.
0
1000
2000
3000
4000
5000
6000
7000
5 10 15 20 25 30 35 40 45 50
Number of tracks
N
um
be
r
of
E
nt
ri
es
Figure 7.4. Monte-Carlo and data distributions of the reconstructed track multiplicity.
The solid line represents the Monte-Carlo and the dots the data.
100
0
1000
2000
3000
4000
5000
6000
7000
8000
0 5 10 15 20 25 30 35 40 45 50
momentum (GeV/c)
E
nt
ri
es
/
1
G
eV
/c
Figure 7.5. Monte-Carlo and data distributions of the momenta of charged hadron tracks.
The solid line represents the Monte-Carlo and the dots the data.
0
2000
4000
6000
8000
10000
0 0.5 1 1.5 2 2.5 3 3.5 4
pT (GeV/c)
E
nt
ri
es
/
50
M
eV
/c
Figure 7.6. Monte-Carlo and data distributions of the pT of charged hadron tracks. The
solid line represents the Monte-Carlo and the dots the data.
101
Figure 7.7 shows the reconstructed background subtracted signals for the J/ψ from
Monte-Carlo and data. Figure 7.8, Figure 7.9, and Figure 7.10 show the reconstructed
background subtracted signals of the Λ0 (and Λ0 ) in the regions near the target/SSDs,
upstream of the dipole magnet, and inside the dipole magnet, respectively. As seen, the
resolution of the reconstructed J/ψ mass and Λ0 (and Λ0 ) from Monte-Carlo are in good
agreement with those from the data.
102
0
100
200
300
400
500
600
700
2.5 3 3.5 4 4.5 5
µ+µ− mass (GeV/c2)
C
om
bi
na
ti
on
s/
(1
0
M
eV
/c
2 )
Figure 7.7. The reconstructed J/ψ signal after background subtraction, the solid line is
from Monte-Carlo and the dots are from data. The Monte-Carlo is normalized to have the
same number of events in the signal region as the data.
103
0
1
2
3
4
5
1.08 1.09 1.1 1.11 1.12 1.13 1.14 1.15
pπ- mass (GeV/c2)
C
om
bi
na
ti
on
s/
1
M
eV
/c
2
Figure 7.8. The reconstructed Λ0 signal after background subtraction for those Λ0 s that
decayed in the target/SSD region. The solid line is from Monte-Carlo and the dots are from
data. The Monte-Carlo is normalized to have the same number of events in the signal
region as the data.
104
0
10
20
30
40
50
60
1.1 1.12 1.14 1.16 1.18 1.2 1.22 1.24
pπ- mass (GeV/c2)
C
om
bi
na
ti
on
s/
2
M
eV
/c
2
Figure 7.9. The reconstructed Λ0 signal after background subtraction for those Λ0s that
decayed upstream of the dipole magnet. The solid line is from Monte-Carlo and the dots
are from data. The Monte-Carlo is normalized to have the same number of events in the
signal region as the data.
105
0
10
20
30
40
50
60
1.1 1.125 1.15 1.175 1.2 1.225 1.25 1.275
pπ- (GeV/c2)
C
om
bi
na
ti
on
s/
3
M
eV
/c
2
Figure 7.10. The reconstructed Λ0 signal after background subtraction for those Λ0s that
decayed inside the dipole magnet. The solid line is from Monte-Carlo and the dots are from
data. The Monte-Carlo is normalized to have the same number of events in the signal
region as the data.
106
7.2 The Λb→ J/ψ Λ
0 search method and results
The topology of the Λb → J/ψ Λ
0
decay is illustrated in Figure 7.11.
Combinatorial background to the Λb signal comes from three sources. The first one is
from p π− and µ+µ− backgrounds underneath the Λ0 and J/ψ signal regions, respectively,
(see Figure 5.1, Figure 6.3, Figure 6.7, and Figure 6.10). The second is from real J/ψ s
combined with real Λ0 s in the same event to give a fake Λb. The third is by wrongly
assigning a proton mass to one of the pion tracks so that a K
0
s → π
+ π- could look like a
Λ0 → p π- (or Λ0 → p π+), since the experiment did not have particle identification
capabilities.
To search for the Λb → J/ψ Λ
0
decay, the (9 + 318 + 285 ) Λ0 (and Λ0 ) candidates
that survived the K
0
s mass cut (see section 6.2.3) were required to have their transverse
µ−
µ+
p
π−
Dipole magnet PWCs
SSDs
x
y
z
r
B
STRAWS
beam Λb
Λ0
primary
vertex
Figure 7.11. The topology of the Λb → J/ψ Λ
0
decay.
107
momenta greater than 0.8 GeV/c. This cut was imposed to filter out Λ0s produced in the
primary interactions. Since Λ0 s originated from Λb s have an average transverse momenta
of 1.3 GeV/c whereas the directly produced Λ0 s had on average transverse momenta of 0.6
GeV/c (see Figure 7.12). This cut reduced the data to 2, 86, and 61 Λ0 (and Λ0 )
candidates, in the target/SSDs, upstream of the dipole magnet, and inside the dipole magnet
regions, respectively. According to Monte-Carlo this cut was 67 %, 75 % and 85 %
efficient in the three regions, respectively.
The Λ0 (and Λ0 ) candidates that survived the transverse monenta cut were then
checked to see if a J/ψ candidate that passed the dimuon refit (see chapter 5) and did not
have its vertex upstream of the primary vertex, was present in the event. This criteria
reduced the Λ0 (and Λ0 ) data sample to (0 + 7 + 8). Table IX shows a summary of the
number of Λ0 (and Λ0 ) candidates that survived each cut employed to reduce to this
number of candidates.
Table IX Summary of the number of Λ0 (and Λ0 ) candidates that survived each cut
employed to select the sample used to search for the Λb → J/ψ Λ
0
decay.
Region Initial
sample
Podolanski-Armenteros
Cut
K
0
s mass
Cut
Λ0-pT
Cut
J/ψ
requirement
I 10 10 9 2 0
II 479 471 318 86 7
III 582 578 285 61 8
108
0
20
40
60
80
100
120
140
160
180
0 0.5 1 1.5 2 2.5 3 3.5 4
Λ0-pT (GeV/c)
E
nt
ri
es
/
0.
25
G
eV
/c
a) Data
0
20
40
60
80
100
0 0.5 1 1.5 2 2.5 3 3.5 4
Λ0-pT (GeV/c)
E
nt
ri
es
/
0.
25
G
eV
/c
b) Monte-Carlo
Figure 7.12. (a) Λ0-pT distribution from data, and (b) from the Λb→ J/ψ Λ
0
Monte-Carlo.
109
The invariant-mass for the (0 + 7 + 8) J/ψ Λ0 combinations summed over the three
reconstruction regions is shown in Figure 7.13 (a), assuming the cuts described above.
The distribution of invariant-mass of Λb s reconstructed from Monte-Carlo simulation is
shown in Figure 7.13 (b). This shows the Λb signal region to be in the range 5.4 GeV/c
2
to
5.9 GeV/c
2
. It is easy to see from Figure 7.13 (a) that there are two events in this mass
range. Thus, there are two Λb → J/ψ Λ
0
candidates. To estimate the shape of the
combinatorial background to this distribution, a "wrong-frame" J/ψ Λ0 background was
produced by combining real J/ψ s with real Λ0 s (and Λ0 s) from different events and
applying the same set of cuts as for the signal. The distribution of invariant mass from
"wrong-frame" events is shown in Figure 7.13 (c). It is clear that the signal region is not
in the same region where the wrong-frame background peaks.
In principle with the data shown so far one can also ask about the B
0
→ J/ψ K0
decay. However, due to the smaller Br(B
0
→ J/ψ K0) (= (7.5 ± 2.1) x 10-4 [12]),
compared to Br(Λb → J/ψ Λ
0
) (= 1.8 x 10
-2
[7]), and F(b → K0 ) (≈ 0.2) compared to F(b
→ Λb ) (≈ 0.1), and considering we can only observe K
0
s and not K
0
L, the expected
number of B
0
→ J/ψ K0 events is about 1/24 of those expected from Λb → J/ψ Λ
0
decays1. Thus, we do not expect to see this decay in our experiment.
1 See chapter 8 for the expected number of Λb → J/ψ Λ
0
decays.
110
0
0.5
1
1.5
2
3 4 5 6 7 8 9
J/ψ Λ0 mass (GeV/c2)
C
om
bi
na
ti
on
s/
5
0
M
eV
/c
2
a) Data
0
10
20
30
40
3 4 5 6 7 8 9
J/ψ Λ0 mass (GeV/c2)
C
om
bi
na
ti
on
s/
5
0
M
eV
/c
2
b) Monte-Carlo
0
500
1000
1500
2000
3 4 5 6 7 8 9
J/ψ Λ0 mass (GeV/c2)
C
om
bi
na
ti
on
s/
5
0
M
eV
/c
2
c) wrong-frame
background
Figure 7.13. (a) The invariant mass for the J/ψ Λ0 combinations; (b) the invariant mass
for the J/ψ Λ0 combinations from Monte-Carlo; (c) J/ψ Λ0 wrong frame background.
111
CHAPTER 8
8. EVALUATION OF THE Λb→ J/ψ Λ
0 PRODUCTION RATE
This chapter gives a detailed explanation of the detection efficiencies for the J/ψs
and Λ0 s, and describes the procedure used to determine an upper limit to the Λb→ J/ψ Λ
0
production rate, F(Λb) * Br(Λb → J/ψ Λ
0
). The upper limit is calculated based on two
events found in the Λb region (see section 7.2). It is then recalculated twice using a
modified set of cuts.
8.1 Acceptances and efficiencies
The acceptances and efficiencies to reconstruct each signal were measured using the
Monte-Carlo summation described in section 7.1. The acceptance for J/ψ → µ+ µ− with xF
> 0 from Λb events is 18 % (see section 7.1). The reconstruction efficiency is 59 % and it
breaks down in the following way:
i. The efficiency of linking each muon throughout the entire detector is 86 %.
112
ii. The invariant mass cut of 2.85 GeV/c
2
< Mµµ < 3.35 GeV/c
2
retains 93% of the
J/ψs.
iii. The dimuon refit to the J/ψ explained in chapter 5 and appendix A is 92 % efficient.
iv. The requirement that the be vertex is not upstream of the primary vertex is 93 %
efficient.
Thus, the reconstruction efficiency for J/ψ → µ+ µ− from Λb events is (0.86)
2
(0.93) (0.92) (0.93) = 0.59. The “PSI” dimuon preselection described in section 4.1.1 is
71 % efficient for J/ψs from Λb s. Therefore, the total detection efficiency for J/ψ s from
Λbs is ε
ψJ from b/ Λ = (0.18)(0.59)(0.71) = 0.075.
The kinematical acceptance, that is the total fraction of the Λ0s that decay in the
three regions once the J/ψ has been accepted is 63%. The individual kinematical acceptance
for each region is 3 %, 25 %, and 35 %, for the target/SSD, upstream of the dipole
magnet, and inside the dipole magnet regions, respectively. The geometrical acceptance
times reconstruction efficiency of Λ0 s in each region is 8 %, 16%, and 29 %, respectively.
After including the K
0
s mass cut which is 90 %, 67% and 49% efficient ( see section
6.2.3), and the Λ0-pT cut on Λ
0
(or Λ0 ) which is 67 %, 75 % and 85 % efficient (see
section 7.2), the geometrical acceptance times reconstruction efficiency of Λ0 s in each
region reduces to 5 %, 8 %, and 12 %, respectively. Therefore, the weighted average total
acceptance times the reconstruction efficiency for the Λ0 once the J/ψ has been accepted is
εΛ
0
= (0.03) (0.05) + (0.25) (0.08) + (0.35) (0.12) = 0.064.
113
8.2 Upper limit on the Λb p roduction rate
The observed number of events in the Λb signal, Nsig, is related to the exclusive
branching ratio Br( Λb → J/ψ Λ
0
) through
Nsig = 2 ε
ψJ from b/ Λ εΛ
0
F(Λb) Br(Λb → J/ψ Λ
0 ) σ
bb
Br(J/ψ → µ+ µ−) Br(Λ0 → pπ-) L, (8.1)
where ε ψJ from b/ Λ is the total J/ψ detection efficiency for J/ψ s originating from Λb s; ε
Λ0
is the total Λ0 detection efficiency; F(Λb) is the production fraction (i.e., the probability of a
b quark to hadronize into a Λb or into another beauty baryon decaying to Λb; Br(Λb → J/ψ
Λ0 ) is the branching ratio for Λb → J/ψ Λ
0
; σ
bb
is the bb production cross-section;
Br(J/ψ → µ+ µ−) is the branching ratio for J/ψ → µ+ µ−; Br(Λ0 → pπ-) is the branching ratio
for Λ0 → pπ- and L is the integrated luminosity. The prompt J/ψ signal from our beryllium
target is used to compute L, this way there is a reduction of systematic uncertainties arising
from efficiency corrections due to dead-time, muon halo, pretrigger and the dimuon trigger
processor. L is written as:
L =
→( )+ −
N
Br J
J
J
J
/
/
/ /
ψ
ψ
ψε σ ψ µ µ
, (8.2)
where εJ/ψ is the total detection efficiency for prompt J/ψ s. In reference [11] we report,
NJ/ψ = 9,800 ± 130 on Be with xF> 0.1. This corresponds to σJ/ψ Br(J/ψ → µ
+ µ−)/Α =
9.2 ± 1.2 nb/nucleon for xF> 0.1 on Be [11]. The acceptance for these J/ψ s with xF > 0.1
is 43%, the reconstruction efficiency is 64 % [11], and the “PSI” dimuon preselection
114
described in section 4.1.1 is 79 %. Thus, the total detection efficiency for prompt J/ψs is
εJ/ψ = (0.43)(0.64)(0.79) = 0.217.
The total detection efficiencies ε ψJ from b/ Λ , εΛ
0
, and εJ/ψ are listed in Table X.
The Br(J/ψ → µ+ µ−) = 5.97 %, and Br (Λ0 → p π-) = 63.9 % [12]. Also E672/E706
measured σ
bb
to be 47 ± 19 (stat) ± 14 (sys) nb/nucleon for xF > 0.0 [11]. From
equations 8.1 and 8.2:
Nsig ε
J/ψ σJ/ψ Br(J/ψ → µ+ µ−)
F(Λb) * Br(Λb → J/ψ Λ
0
) = . (8.3)
ΝJ/ψ 2 ε
ψJ from b/ Λ εΛ
0
σ
bb
Br(J/ψ → µ+ µ−) Br (Λ0 → p π-)
To compute an upper limit to F(Λb) * Br(Λb → J/ψ Λ
0
), the 2 events in the Λb
signal region (see section 7.2) are treated as signal with zero background. According to
Poisson statistics the maximum number of signal events that the 2 events can statistically
fluctuate up to is 5.3 events at the 90 % C.L1. Therefore
F(Λb) * Br(Λb → J/ψ Λ
0
) < 6.2 x 10
-2
at 90 % C.L.
This does not contradict the value measured by UA1 of F(Λb) * Br(Λb → J/ψ Λ
0
) = 1.8 ±
1.1 x 10
-3
[7]. Using the UA1 measurement and the set of cuts described in the previous
chapters we expect to find 0.2 Λb → J/ψ Λ
0
events. To better understand and measure the
F(Λb) * Br(Λb → J/ψ Λ
0
) upper limit, this number was recalculated twice under a modified
set of cuts than those used above.
1 See ref. [12] page 1279
115
The first set was made without including the K
0
s mass cut mentioned in section
6.2.3. Without this cut the Λ0 total detection efficiency εΛ
0
= (0.03) (0.05) + (0.25)
(0.12) + (0.35) (0.25) = 0.119 (see section 8.1 for the definition of each factor).
Consequently removing this cut, the Λ0 total detection efficiency increases approximately
by a factor of 2 and therefore increases the expected number of Λb signal events to about
0.4 events, maximizing the signal. Without the K
0
s mass cut, the Λ
0
(or Λ0 ) data sample
contains 10, 471, and 578 candidates in the target/SSD, upstream of the dipole magnet, and
inside the dipole magnet regions, respectively (see section 6.2.3 for all other cuts applied).
Applying the cut Λ0-pT to be greater than 0.8 GeV/c reduces the data sample to 2, 122, and
162 candidates in the three regions, respectively (see section 7.2 for the motivation of this
cut). After searching each event in this data sample for a J/ψ candidate that passed the
dimuon refit (see chapter 5) and did not have its vertex upstream of the primary vertex, the
Λ0 (and Λ0 ) data sample reduced to (1 + 22 + 25) events. The invariant-mass for these 48
J/ψ Λ0 combinations is shown in Figure 8.1 with the solid line. The dashed line represents
1 This value is the weighted average acceptance times reconstruction efficiency for the
Λ
0
(and Λ0) in the three reconstruction regions combined, once the J/ψ has been accepted.
Table X. The total detection efficiencies for the different particles, which are the products
the kinematical and geometrical acceptance, reconstruction efficiencie and preselection
efficiencie.
Acceptance
(%)
Reconstruction
efficiency (%)
Preselection
efficiency (%)
Total detection
efficiency (%)
J/ψ s from Λbs 18 59 71 ε
ψJ from b/ Λ = 7.5
prompt J/ψs 43 64 79 εJ/ψ = 21.7
Λ0(and) Λ0 6.4
1
εΛ
0
= 6.4
116
wrong-frame background normalized to have the same number of events in the region
between 6.5 GeV/c
2
and 9.0 GeV/c
2
as the data. Recall that the Λb signal region is the
mass interval between 5.4 GeV/c
2
and 5.9 GeV/c
2
. There are 7 Λb candidates in this signal
region (number of events observed), and 12 background events in the wrong-frame
background (number of expected background events). According to Poisson statistics, the
maximum number of signal events that 7 observed events with an expected background of
12 events, can fluctuate up to is 4.2 events at the 90 % C.L1. Using equation 8.3 were
every value is the same expect for εΛ
0
which is now 0.119, one finds that
F(Λb) Br(Λb → J/ψ Λ
0
) < 3.1 x 10
-2
at 90 % C.L.
The second set of cuts also does not included the K
0
s mass cut, but in addition the
J/ψs are required to originate from a vertex downstream of the primary vertex in the event.
In this set of cuts the background is reduced to a minimum. The reconstruction of J/ψ s
with xF > 0 from Λb events is now (0.86)
2
(0.93) (0.92) (0.60) = 0.38 (see section 8.1 for
the definition of each factor). Thus, ε ψJ from b/ Λ = (0.18)(0.38)(0.71) = 0.048. Giving an
expected number of event of about 0.2. Requiring that the J/ψ s emerge from secondary
vertices, reduces J/ψ Λ0 data sample to (1 + 1 + 2) events. The requirements for a J/ψ to
be originated from a secondary vertex are the same as those used in the J/ψ selection
process for our bb cross-section calculation in [11]. (i) The primary vertex in the event is
required to have at least 3 SSD-PWC linked tracks associated with the vertex. (ii) The J/ψ
vertex is required to be at least 2.5 mm downstream of the primary vertex, and (iii) a
1 See ref. [12] page 1279
117
significance greater than 3 is required for both longitudinal and transverse separations
between the primary and secondary vertex, with the significance defined as the separation
divided by the combined uncertainty. The invariant-mass for the (1 + 1 + 2) J/ψ Λ0
combinations is shown in Figure 8.2. There are no events in the Λb signal region. For the
purpose of computing an upper limit to F(Λb) * Br(Λb → J/ψ Λ
0
), the signal is zero and
the is zero background. According to Poisson statistics, the maximum number of signal
events that zero signal and zero background can statistically fluctuate up to is 2.3 events at
the 90 % C.L 1. Using equation 8.3 as before but with ε ψJ from b/ Λ = 0.038, one gets
F(Λb) * Br(Λb → J/ψ Λ
0
) < 3.2 x 10
-2
at 90 % C.L.
1 See ref. [12] page 1279
118
0
0.5
1
1.5
2
2.5
3
3 4 5 6 7 8 9
J/ψ Λ0 (GeV/c2)
C
om
bi
na
ti
on
s/
5
0
M
eV
/c
2
Figure 8.1. The invariant mass distribution (solid) for the J/ψ Λ0 combinations, without
using the K
0
s mass cut, and the wrong-frame background (dashed).
119
0
0.2
0.4
0.6
0.8
1
3 4 5 6 7 8 9
J/ψ Λ0 mass (GeV/c2)
C
om
bi
na
ti
on
s/
5
0
M
eV
/c
2
Figure 8.2. The invariant-mass distribution for the J/ψ Λ0 combinations, without using
the K
0
s mass cut, and requiring that the J/ψ s originate from secondary vertices.
120
CHAPTER 9
1. CONCLUSIONS
An extensive analysis was performed on 8.0 pb
-1
of dimuon data produced in π− A
collisions at 515 GeV/c to search for Λb events in the decay channel Λb → J/ψ Λ
0
, with J/ψ
→ µ+ µ− and Λ0 → p π− (and for the conjugate reactions). A refit to the muon tracks from
J/ψ decays was performed with the mass constraint of two-body decay and with the
constraint that both muon tracks intersect at a common point. The Λ0 s were identified by
their characteristic decay, giving the larger fraction of their momenta to the protons. Using
an iterating algorithm, Λ0 s were reconstructed in three regions of the E672/E706
spectrometer, near the target/SSDs, between the SSDs and the dipole magnet, and inside
the dipole magnet. A total of 575 ± 35 Λ0 (and Λ0 ) background subtracted events were
reconstructed. A K
0
s → π
+ π− signal was also reconstructed in all three regions using the
same technique. The K
0
s mass signal was used to cross-check the reconstruction algorithm
and to clean the Λ0 (and Λ0 ) data sample, giving (9 + 318 + 285) Λ0 (and Λ0 ) candidates.
To search for the Λb → J/ψ Λ
0
(and charge conjugate reaction), J/ψ s that passed
the muon refit were combined with clean Λ0 s (or Λ0 s) when they existed in the same
121
event, giving a total of (0 + 7 + 8) J/ψ Λ0 (and charge conjugate) combinations. The
results show 2 events in the Λb mass region. Considering the two Λb events as signal with
zero background, an upper limit to F(Λb) * Br(Λb → J/ψ Λ
0
) was found to be less than
6.2 x10
-2
at 90 % C.L. An upper limit was also calculated, without using the K
0
s mass cut
for the Λ0 s (and Λ0 s), then, also requiring that the J/ψ s originate from secondary
vertices, giving that F(Λb) * Br(Λb → J/ψ Λ
0
) < 3.1 x10
-2
at 90 % C.L and F(Λb) *
Br(Λb → J/ψ Λ
0
) < 3.2 x10
-2
at 90 % C.L, respectively. The upper limits should be
compared to (1.8 ± 1.1) x 10-3 measured by UA1 [7].
This study was performed using a Monte-Carlo simulation for bb production from
next-to-leading order (NLO) calculations of Mango, Nason, and Rodolfi (MNR), which
included the mass factorization scale Q = mb/2, the ΛQCD = Λ5 = 204 MeV, and the
MRS235 and SMRS parton distribution functions for the nucleon and pion, respectively
[21]. In addition It was assumed that the Λb s are unpolaraized, and no fragmentation was
included.
In conclusion E672 did not have the sufficient sensitivity to contradict the UA1
measurement, nor give a lower limit than the ones established by ALEPH (< 0.4 x 10
-3
at
90 % C.L.), OPAL (< 1.5 x10
-3
90 % C.L.), and CDF (< 0.5 x 10
-3
at 90 % C.L.), (see
Refs. [8] and [9]). However, ALEPH and OPAL both used e
+
e
−
interactions, UA1 and
CDF used pp interactions , and CDF had a limited sensitivity to reconstruct Λ0 s (and Λ0 s)
that have a π− (and π+) with pT < 0.4 GeV/c [9]. Here we used π
−
A collisions and
reconstructed Λ0 s (and Λ0 s) with the pT of the π
−
(and π+) between 0 GeV/c and 0.4
122
GeV/c. Thus, our search for the Λb → J/ψ Λ
0
(and charge conjugate reaction) in
complementary to that of the others mentioned above.
123
APPENDIX A
FIT TO THE J/ψ
The muons that form the decaying J/ψ are fitted using a Least-Squares method
(explained in detail below) with the constraint that the two muons intersect at a common
point in space and that the invariant mass of the combined pair is equal to 3.097 GeV/c
2 1 .
The χ2 of the fit is used to reduce the combinatorial background when there are more than
two muon candidates in a given event. The fit improves the resolution of the measured
momenta of the muons by a factor of 2 and vertex position by 15%.
General least-squares estimation with constraints
The mathematical formulation of the iterative procedure will be derived without
making any reference to any special physical problem.
1 This is the value published by [12].
124
The iteration procedure
Let
r
M = m1,m2 ,...,mN{ }be a vector of N measurable variables, which have initial
measurements
r
M0 = m1
0 ,m2
0 ,...,mN
0{ } , with errors contained in the covariance matrix
E(
r
Mo ) . In addition, let
r
U = u1,u2 ,...,uJ{ } be a set of J unmeasurable variables. The
r
M variables and the
r
U variables are related and have to satisfy a set of K constraint
equations
f k (m1,m2 , . . . ,mN ,u1,u2 , . . . ,uJ ) = 0 , k = 1,2, . . . ,K .
According to the Least-Squares Principle, the best estimates of the
r
M and
r
U
variables are those for which
χ2
r
M,
r
Mo( ) = rMo − rM( )T E−1 rMo( ) rMo − rM( ) = min imum , and (Α.1)
r r r r
f M U,( ) = 0,
where the superscript T indicates the transpose of the matrix.
The problem will now be solved using the Lagrange multiplier method.
Introducing the K component vector
r
λ = λ1,λ2 ,...,λK{ } of Lagrangian multipliers, the
problem can be rephrased by requiring
χ2
r
M,
r
U,
r
λ( ) = rMo − rM( )T E−1 rMo( ) rMo − rM( ) + 2
r
λT
r
f
r
M,
r
U( ) = min imum . (A.2)
125
There are now a total N+J+K variables. The values of
r
M ,
r
U and
r
λ that make the
χ2 minimum, must also satisfy the following set of equations
∇M χ
2 = −2 E−1
r
Mo( ) rMo − rM( ) + 2 FMT
r
λ =
r
0, (N equations)
∇U χ
2 = 2 FU
T
r
λ =
r
0, (J equations) (A.3)
∇λχ
2 = 2
r
f
r
M,
r
U( ) =
r
0 , (K equations)
where the matrices FM ,FU of dimensions KxN and KxJ respectively are defined by
FM( )k i ≡
∂f k
∂m i
, FU( )k j ≡
∂f k
∂u j
.
Simplifying equations (A.3) gives
− ( ) −( ) + =−E M M M FMT1 0 0 0
r r r r r
λ , (A.4a)
FU
T
r
λ =
r
0, (A.4b)
r
f
r
M,
r
U( ) =
r
0 . (A.4c)
The solution to the set of equations (A.4) for the N+J+K variables must be, in
general, found by iterations producing successively better approximations. To do this,
suppose that the n-th iteration has been performed and it is still necessary to find a better
solution. For the n-th iteration the approximate solution is given by the values of
126
r
Mn ,
r
Un ,
r
λn , corresponding to the function value (χ
2 )n . By performing a Taylor expansion
of the constraint equations (A.4c) about the point
(
r
Mn ,
r
Un ) one obtains:
f k
n +
∂f k
∂m i
i=1
N
∑
n
(m i
n+1 − m i
n ) −
∂f k
∂u i
j=1
J
∑
n
(u j
n+1 − u j
n ) + ...= 0 , k = 1,2,...,K.
Neglecting all terms of second or higher order, this equation can be written as
r
f n + FM
n
r
Mn+1 −
r
Mn( ) + FUn
r
Un+1 −
r
Un( ) =
r
0 , (A.5)
where all superscripts n indicate that the
r
f n ,FM
n ,FU
n are to be evaluated at the point
(
r
Mn ,
r
Un ). The other two equations in A.4, a and b, are then,
E−1
r
Mn+1 −
r
M0( ) + FMT( )n
r
λn+1 =
r
0, (A.6a)
FU
T( )n
r
λn+1 =
r
0 . (A.6b)
These two equations, together with the expanded constraint equations (A.5) make it
possible to express all variables of the (n+1)-th iteration in terms of quantities of the
preceding iteration. These solutions are
r
Un+1 =
r
Un − FU
T S−1 FU( )
−1
FU
T S−1
r
r ,
r
λn+1 = S−1
r
r + FU
r
Un+1 −
r
Un( )[ ] , (A.7)
r
Mn+1 =
r
M0 − E FM
T
r
λn+1 ,
127
where
r
r =
r
f n + FM
n
r
M0 −
r
Mn( ) ,
S ≡ FM
n E FM
T( )n .
In equations (A.7) the matrices
FM ,FU ,S, and the vector
r
r are evaluated at the point
(
r
Mn ,
r
Un ). The value of
r
U0 can be found from the set of the constraint equation, setting
r
f
r
M0 ,
r
U0( ) = 0 and solving for
r
U0 . With the new values for
r
Mn+1,
r
Un+1 and
r
λn+1 one can
calculate the value of the function χ2( )n+1 for the (n+1)-th iteration and compare it with the
previous value of χ2( )n , by using
χ2( )n+1 =
r
λn+1( )T S
r
λn+1 + 2
r
λn+1( )T rf n+1, (A.8)
where the matrix S is evaluated for the n-iteration. Once a satisfactory solution is found the
iterative procedure is stopped. This is when the value of the χ
2
and the values of the
r
M and
r
U vectors are converging [54].
Kinematical analysis of the J/ψ → µ+µ− decay
The following section applies the previous formulation to the J/ψ → µ+µ− decays
as seen in the MWEST spectrometer. Let us assume that the two muon tracks have been
measured and that the track reconstruction program has provided for each muon track a
first approximation for the kinematical variables: 1/p ( inverse momentum); mx (track slope
in the x-z plane ); my (track slope in the y-z plane ); bx (intercept of the track with the x-axis
in the x-z plane); and by (intercept of the track with the y-axis in the y-z plane); as well as a
covariance matrix (E) for these values. Since the decay vertex of the J/ψ (x, y, z) is
128
unspecified and the magnitude and direction of its momentum is unknown, the problem in
this case involves six unmeasurable variables
r
U =
1
pJ / ψ
,mx J / ψ ,my J / ψ ,x,y,z
,
and ten measurable variables for both muon tracks,
r
M =
1
p
µ +
,m
x µ +
,m
y µ +
,b
x µ +
,b
y µ +
,
1
p
µ −
,m
x µ −
,m
y µ −
,b
x µ −
,b
y µ −
.
The algebraic constraint equations are: the three equations describing momentum
conservation; the equation from energy conservation; and the geometrical line-equations of
the tracks in the x-z and y-z planes. This gives a total of eight equations:
f1 = −
mx J / ψ
1
pJ / ψ
mx J / ψ
2 + my J / ψ
2 + 1
+
m
x µ +
1
p
µ +
m
x µ +
2 + m
y µ +
2 + 1
+
m
x µ −
1
p
µ −
m
x µ −
2 + m
y µ −
2 + 1 ;
f 2 = −
my J / ψ
1
pJ / ψ
mx J / ψ
2 + my J / ψ
2 + 1
+
m
y µ +
1
p
µ +
m
x µ +
2 + m
y µ +
2 + 1
+
m
y µ −
1
p
µ −
m
x µ −
2 + m
y µ −
2 + 1 ;
f
p
m m
p
m m
p
m m
J
x J y J x x x x
3
2 2 2 2 2 2
1
1
1
1
1
1
1
1
1
= −
+ +
+
+ +
+
+ +
+
+ +
−
− −
/
/ /
ψ
ψ ψ
µ
µ µ
µ
µ µ
;
f 4 = −
1
1
pJ / ψ
2 + mJ / ψ
2 +
1
1
p
µ +
2 + mµ
2 +
1
1
p
µ −
2 + mµ
2
;
f 5 = −x + z mx µ + + bx µ + ;
129
f 6 = −x + z mx µ − + bx µ− ;
f 7 = −y + z my µ + + by µ + ;
f 8 = −y + z my µ − + by µ − ;
where mJ / ψ and mµ are the masses of the J/ψ and muon, respectively. Since the problem
involves 8 constraint equations and 6 unmeasurable variables this is then a 2c-fit.
Results from the fit
In a given event, all the unlike-sign muon pairs with fully linked SSD-PWC-
MUON tracks, and with an invariant-mass in the mass interval between 2.85 GeV/c
2
to
3.35 GeV/c
2
, and having a distance of closest approach between the two muon tracks less
then 50 µm, were fitted with the above technique. For convergence, the values of the χ2,
r
M, and
r
U variables were required to be within 0.001 of the preceding values of each
variable, respectively. In each event only the dimuon with the lowest χ2 was kept. Figure
A. 1 shows the distribution of the χ2 per degree of freedom of the fit. A cut on the
χ2/d.o.f less than 5.0 was established. Before the fit, there were a total of 13,053 muon
pairs. After the fit 12,340 dimuons survived the fit requirements. These were identified as
J/ψ s.
From the Λb →J/ψ Λ
0
Monte-Carlo, the reconstruction efficiency of the initial track
finding for J/ψ s from Λb s was found to be 49.8 %, and by using the refit procedure this
efficiency was improved to 59 %. In Figure A. 2 the dashed line shows the residuals of
the J/ψ momentum between the generated value from Λb →J/ψ Λ
0
Monte-Carlo and that
130
reconstructed by the initial track finding. The solid line shows the residuals of the
momentum after the refit. Figure A. 3 shows the residuals of the z-coordinate of the J/ψ
decay vertex between the generated value from Monte-Carlo and the reconstructed, the
dashed line for the initial track finding and the solid line for the refit. As one can see,
refitting the J/ψ resulted in an improvement of its momentum measurement resolution by a
factor of 2, and in the vertex resolution by 15%.
131
χ2 per degree of freedom
0
50
100
150
200
250
0 1 2 3 4 5 6 7 8 9 10
N
um
be
r
of
E
ve
nt
s
Figure A. 1. The χ
2
per degree of freedom distribution from the J/ψ refit.
132
0
50
100
150
200
250
300
350
-40 -30 -20 -10 0 10 20 30 40
(GeV/c)
E
ve
nt
s/
4
00
M
eV
/c
J/ψ momentum residuals
Figure A. 2. Residuals of the J/ψ momentum between the generated momentum value in
the Λb→ J/ψ Λ
0
Monte-Carlo and the reconstructed value. The dashed line is for the
values reconstructed by the initial track finding. The solid line shows the residuals of the
momentum after the refit.
133
0
20
40
60
80
100
120
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
J/ψ z-coordinate vertex residuals (µm)
E
ve
nt
s/
0
.1
m
m
Figure A. 3. Residuals of the z-coordinate of the decay vertex between the value generated
in the Monte-Carlo and the value reconstructed. The dashed line is for the values found by
the initial track finding and the solid is for those after the refit.
134
APPENDIX B
MOMENTUM MEASUREMENT IN THE REGION UPSTREAM
OF THE DIPOLE MAGNET
Assuming the decay vertex of the Λ0 (x, y, z) and the parameters of the PWC track
mxD (x-slope), myD (y-slope), bx (x-intercept) by (y-intercept) are known, and that the
magnetic field is uniform throughout the dipole magnet,
r r
B B j= − ˆ. The momentum vector
is estimated in the following way: First, the coordinates of the PWC track at the center of
the magnet are computed,
zcenter = 197.73 cm,
xcenter = zcenter + bx,
Then, to estimate the bend of the trajectory of particle (proton or pion), the x-slope
mxU of the imaginary line in the x-z plane from (x, z) to (xcenter, zcenter) is computed
m
x x
z z
xU
center
center
=
−
−
,
135
see Figure B. 1. MxU is the slope of the proton or pion trajectory at the Λ
0
decay vertex.
Since the magnetic field is along the negative y-axis (see section 2.5.2) the electric charge
associated with the track is then,
Q
m m
m m
xD xU
xD xU
=
−
−
.
The magnitude of the momentum of the track in the x-z plane is:
P
P
m
m
m
m
xz
T
xD
xD
xU
xU
kick=
+
−
+
v
1 12 2
,
where
v r
P BTkick = 0 3. L , and
r
B is the magnetic field (in Tesla), and L (in meters) is the
length of the field along the z-axis. From Pxz one can calculate the z component of the
momentum:
P
P
m
z
xz
xU
=
+1 2
;
and from this the x and y components:
Px = Pz mxU;
and
Py = Pz myD.
136
Dipole Magnet
(x,z)
(xcenter,zcenter)
Tan-1(mxU)
Tan-1(mxD)
x
y z
Proton or pion PWC track
Figure B. 1. The thin lens approximation is used to compute the momenta of the proton
and pion tracks of those Λ0 s that decayed upstream of the dipole magnet.
137
APPENDIX C
MOMENTUM MEASUREMENT IN THE REGION INSIDE THE
DIPOLE MAGNET
Assuming that the decay vertex of the Λ0 (x,y,z), and the parameters of the PWC
track mxD (x-slope), myD (y-slope), bx (x-intercept), by (y-intercept) are known, and that
the magnetic field is uniform throughout the dipole magnet,
r r
B B j= − ˆ. The magnitude of
the momentum is determined by measuring the radius R of the circular trajectory described
by the proton or pion particle inside the magnetic field. R is related to the momentum of the
particle in the x-z plane by,
r r
P B Rxz = 0 3. , where
r
B is measured in Tesla, and R in
meters. The momentum vector is estimated in the following way: Labeling the center of the
circular trajectory as (xo, zo), see Figure C. 1, it is easy to see that,
x x z z Ro o−( ) + −( ) =
2 2 2 ;
x x z z Rend o end o−( ) + −( ) =
2 2 2 ; and
m
x x
z z
xD
end o
end o
⋅
−
−
= −1;
where, zend = 318.53 cm, and xend = mxD+ bx.
138
Dipole Magnet
(x,z)
(x
o
,z
o
)
Tan-1(mxD)
x
y z
PWC proton or pion track
(xend,zend)
R
Tan-1(mxU)
Figure C. 1. Circular trajectory described by of a proton or pion of a Λ0 that decays inside
the dipole magnet.
These three equations have three unknowns, xo, zo, and R. It is not so difficult to
solve for these unknown variables and obtain
z z
x x z z
x x
m
z z
o end
end end
end
xD
end
= −
−( ) + −( )
−( )
− −( )
1
2
2 2
;
x x
m
z zo end
xD
end o= + −( )
1
; and
139
R
m
z z
xD
end o= +
−( )1 12 .
Having this, mxU can now be computed,
m
z z
x x
xU
o
o
=
−
−
,
and the electric charge of the particle is found,
Q
m m
m m
xD xU
xD xU
=
−
−
.
As mentioned previously the momentum of the particle in the x-z plane is
r r
P B Rxz = 0 3. , .
From Pxz one can calculate the z component of the momentum:
P
P
m
z
xz
xU
=
+1 2
;
and from this the x and y components:
Px = Pz mxU;
and
Py = Pz myD.
140
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145
Francisco J. Vaca
8821 S. Escanaba
Chicago, IL 60617
(312) 933-4751
University of Illinois at Chicago
Department of Physics, M/C 273
845 W. Taylor St., Room 2263
Chicago, IL 60607
(312) 996-6751
FAX: (312) 996-9016
Internet E-Mail: [email protected]
P e r s o n a l
Date of Birth: April 2, 1968
Place of Birth: Zamora, Michoacán, México
Nationality: US
Marital status: Married, one child
Languages: English and Spanish
E d u c a t i o n
Universidad Michoacana
Morelia, Michoacán, México
B.S. degree in Physics and Mathematics, Dissertation: Maximization of Power in
Thermodynamic and Biological cycles.
University of Illinois at Chicago
Chicago, IL
M.S. degree in Physics
University of Illinois at Chicago
Chicago, IL
Ph.D. degree in Physics, Dissertation: Search for Λb in π
- N collisions at 515 GeV.
A c a d e m i c A c h i e v e m e n t s a n d D i s t i n c t i o n s
1985-1989 Scholarship from the Universidad Michoacana, México
1991 President, Society of Physics Students, UIC Chapter
1991 Sigma Pi Sigma (Physics Honors Society), UIC Chapter,
Recognition
1989-1992 Illinois Minority Graduate Incentive Program Fellowship
1992 Latino Committee at UIC, Recognition
1992-1993 Martin Luther King, Jr. Award, UIC
VITA
1985 - 1989
1989 - 1992
1989 - 1995
146
1993 First Prize award, International Committee for Future
Accelerators India School on Instrumentation in Elementary
Particle Physics (ICFA 93), Bombay, 15-27 Feb. 1993
1993-1994 University of Illinois at Chicago Graduate Fellowship
1993-1994 National Hispanic Scholarship Foundation Scholarship
1994-1995 University of Illinois at Chicago Graduate Fellowship
1994-1995 National Hispanic Scholarship Foundation Scholarship
S u m m e r s S c h o o l s A t t e n d e d
• Universidad Autónoma de México Molecular Vision of Matter Summer School, Cuernavaca,
Morelos, México, 1-30 Aug. 1988
• International Committee for Future Accelerators India School on Instrumentation in
Elementary Particle Physics (ICFA 93), Bombay, February 15-27, 1993
• Advanced Study Institute on Techniques and Concepts of High Energy Physics (ASI 94), St.
Croix, USVI, June 16-27, 1994
• Lafex International School on High Energy Physics (LISHEP 95), Rio de Janeiro, February 6-
22, 1995
P r o f e s s i o n a l A f f i l i a t i o n s
1989 - present Society of Physics Students, UIC chapter
1991 - present American Physical Society, Division of Particles and Fields
P r o f e s s i o n a l E x p e r i e n c e
Universidad Michoacana
Morelia, Michoacán, México
Teaching Assistant, Assisted in teaching undergraduate courses (calculus, linear algebra)
University of Illinois at Chicago
Chicago, IL
Teaching Assistant,Taught undergraduate physics laboratories
University of Illinois at Chicago
Chicago, IL
Research Assistant, Research assistant with high-energy physics group working on Fermilab
experiment E672
University of Illinois at Chicago
Chicago, IL
Supplemental Instructor, Engineering College, Minority Engineering Recruitment and
Retention Program: tutor for undergraduate physics
1986- 1989
1989 - 1994
1991 - 1994
1994 - 1995
147
University of Illinois at Chicago
Chicago, IL
Consultant, Engineering College, Minority Engineering Recruitment and Retention Program:
participated as the content expert in the creation of videos on undergraduate physics topics
Columbia College Chicago
Chicago, IL
Part-time Faculty, teaching undergraduate physics class and laboratory
P r e s e n t a t i o n s
• "Fermilab Experiment E672", poster session, annual Department of Energy review of the
Fermilab physics program, Fermilab, Mar. 29, 1994.
• "Charmonium Production and a Search for Λb in Fermilab E672/E706", American Physical
Society April Meeting, Washington DC, April 18-21, 1995.
P u b l i c a t i o n s
A. Gribushin et al., “Production of J/ψ and ψ(2S) Mesons in π- Be Collisions at 515 GeV/c”,
FERMILAB-Pub-95/298-E, Sep. 1995, submitted to Phys. Rev. D.
R. Jesik et al., "Bottom Production in π- -Be Collision at 515 GeV/c", Phys. Rev. Lett. 74, 459
(1995).
R. Jesik et al., "Hadronic Production of Beauty", Proceedings of the XXVIII Rencontres de
Moriond, Les Arcs, France, Mar. 20-27, 1993, p. 385.
L. Dauwe et al., "Hadronic Production of B Mesons", Proceedings of the 1992 A.P.S.
Division of Particles and Fields Meeting, Batavia, IL, Nov. 9-14, 1992, p. 759.
H. Mendez et al., "Hadronic Production of χc Mesons", Proceedings of the 1992 A.P.S.
Division of Particles and Fields Meeting, Batavia, IL, Nov. 9-14, 1992, p. 756.
R. Jesik et al., "Heavy Flavor Production in π--A Collisions at 530 GeV/c", Proceedings of the
XXVI International Conference on High Energy Physics, Dallas, TX, Aug. 5-12, 1992, ed. J.
Stanford (American Institute of Physics, 1993), p. 824.
A. Zieminski et al., "Production of χc States in π
-- Nucleus Collisions at 530 GeV/c",
Proceedings of the XXVI International Conference on High Energy Physics, Dallas, TX, Aug.
5-12, 1992, ed. J. Stanford (American Institute of Physics, 1993), p. 1062.
R. Li et al., "Hadroproduction of Vector Mesons and χc States", Proceedings of the XXVII
Rencontres de Moriond, Les Arcs, France, Mar 21-28, 1992, p. 385.
B. Abbott et al., "Effects of a Hadron Irradiation on Scintillating Fibers", IEEE Trans. Nucl. Sci.
40, 476 (1993).
1994
1993 -1995
148
I n P r e s s
A. Gribushin et al., "Hadronic production of Heavy Quarks", to be published in the
Proceedings of the XXIX Rencontres de Moriond, Les Arcs, France, Mar 20-27, 1994.
H. Mendez et al., " Hadroproduction of Charmonium States ", to be published in the
Proceedings of the XXX Rencontres de Moriond, Les Arcs, France, Mar 19-26, 1995
I n P r e p a r a t i o n
V. Koreshev et al., “Production of Charmonium States in π- Be Collisions at 515 GeV/c”.
F. Vaca et al., “Production of Vector Mesons in Hadron-A Interactions”.
| 0non-cybersec
| arXiv |
Does $p$ integrability in n-1 dimensions give higher integrability in $n$ dimensions?. <p>Restrict everything to a ball in $n$ dimensions, let $x$ represent the first $n-1$ variables, and $t$ the $n-$th variable. It is obvious by Holder's Inequality that
$$
\int\limits_t\left(\int\limits_x|f|^p\right)^{\frac1p}\leq\left(\int\limits_t\int\limits_x|f|^p\right)^{\frac1p}|\{f\neq0\}|^{1-\frac1p}
$$
I am interested in whether the following inequality holds</p>
<p>$$
\int\limits_t\left(\int\limits_x|f|^p\right)^{\frac1p}\leq C\left(\int\limits_t\int\limits_x|f|^{p-\epsilon}\right)^{\frac1{p-\epsilon}}
$$
for $\epsilon>0$ and $f$ such that $\Vert f\Vert_{L^p(x)}$ and $\Vert f\Vert_{L^p(x,t)}$ are small ($<1$ in particular). Any results related to this question are welcome.</p>
| 0non-cybersec
| Stackexchange |
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