## LHC takes hadron collider luminosity record

Until yesterday the highest luminosity measured in a hadron collider was 402.4/μb/s achieved at the Tevatron last year. Last night the Large Hadron Collider smashed this record with a luminosity of 481/μb/s using a 480 bunch filling scheme. This takes them nearly half way to this years target of 1/nb/s . In fact they are likely to reach that level in the next few weeks and can go well beyond if they stick to the 50ns bunch spacing.

The superior energy of the LHC over the Tevatron means that it now has every advantage. Strong hints of new physics from about 70/pb of collision data are already showing up, yet CERN could collect 200 times that amount before the end of 2011. This could be a good year to be doing particle physics! (The data collected in 2011 now amounts to 90/pb in each of ATLAS and CMS to add to the 40/pb from 2010)

CERNs new record follows a visit on Wednesday by Jose Barosso, president of the European Commission who said “CERN is a true European centre of excellence: a place where our collective talent is pooled and produces cutting-edge research, European in its foundations but global in its outlook.”

Update 23-Apr-2011: The latest run collected a record 15/pb taking this year’s total to over 100/pb. Until at least Monday they plan to stay with 480 bunches. At this level they should collect 20/pb per day. With about 150 days of proton physics left this year that would already provide 3/fb. However it will probably not be long before they continue to push up the luminosity. Another factor of four should be possible if they can go all the way to 1404 bunches and use nominal intensities.

Update 27-Apr-2011: Now they are filling with 624 bunches. This could take luminosities up to 750/μb/s

### 26 Responses to LHC takes hadron collider luminosity record

1. Luboš Motl says:

If you were following the counter on my blog, you would know that the record is already 520/ub/s now (for ATLAS). ;-)

• Philip Gibbs says:

Yes that came just after my update, but I can’t leave the beach to report every new record as it happens :)

• carla says:

lubos, you’ve room to talk since your counter records the integrated luminosity as 110pb whereas now its almost 140pb and probably near 155pb after the current run ;)

• Luboš Motl says:

Thanks, Carla, will update now. If there’s still no SUSY in this 155/pb, it will gradually start to reduce my optimistic expectations which hasn’t been the case so far. :-)

• Philip Gibbs says:

The figure of 110/pb would have been correct for integrated luminosity collected this year. That stood at 107/pb at the beginning of the current fill with 7/pb coolected so far during this fill. The 40/pb from last year can also be added. Perhaps Lubos could clarify which figure he is tracking.

• carla says:

Even with the cryo problem, they still managed to collect another 13/pb compared to 25/pb, so bringing the integrated luninosity to 203/pb. So at this rate, they are averaging at least 100/pb per week. On the other hand, I’ve noticed that every month, a few days are set aside for a technical stop and machine development which will affect the amount of date collected each month.

Even though it appears the proton run runs to to end of October, giving 6 months in total, there are really only 5 months of data collection it seems.

• Philip Gibbs says:

They have every day counted and are expecting 124 days of physics runs once they have completed the stage of building up luminosity. They have about 20 days of physics left before that 124 days start, during which they will try to increase luminosity by another factor of two at least. Amazingly they could just about reach the original 1/fb target before the beginning of June when the 124 days starts. But they can loose days especially when they have problems recovering from the technical stop as they did last time.

Tomorrow they intend to increase to 624 bunches.

• carla says:

Will they be leaving the luminosity unchanged for the 124 days or continue to push it?

As well as cryo problems, they now seem to have literacy problems:

Sometimes even physicists can’t spell physics correctly

• Philip Gibbs says:

The plan was to run with same parameters for 124 days. They never stick to plan but once they get to 1404 bunches with best intensity bunches there will not be much more they can do to increase it further.

• Philip Gibbs says:

ATLAS recorded 535/ub/s yesterday and that is about to be beaten. However Paul Collier has said that the ATLAS luminosity reading is probably too high and will be recalibrated with a VdM scan after the next technical stop. Until then we should consider the CMS value for luminosity as more reliable

• carla says:

Wouldn’t it be possible to calculate the instantaneous luminosity from the integrated luminosity and time of run?

2. carla says:

On Saturday, they managed to collect 25/pb in one run which is a massive improvement on the 15/pb record the day before.

I’m addicted to watching the Atlas status page, keeping my fingers crossed that the beams don’t die out after 10 hours so that the luminosity can be ramped up further in future.

Anyone know if some sort of counselling for LHC beam addicts is available? :)

• Philip Gibbs says:

I’ll join you in the rehab clinic :)

The Easter weekend seems to have been used partly as an opportunity to see how efficiently they can run when they stick at one level, (although they are also changing the injection from 36 to 72 bunches) The answer is “very efficiently” it seems

• carla says:

What are the options available for maximising the *integrated* rather than instantaneous luminosity for a run?

For example, for an 18 hour total run, would they be better off dividing it into two 9 hour runs?

To increase the instantaneous luminosity for a run, do the beams have to be dumped, or can the intensity of the current beams be increased on the fly?

After a beam dump, how long does it take to ramp up the beam?

• Philip Gibbs says:

They can’t add more protons in the middle of a run because they can’t inject at 3.5 TeV. They have to dump and recycle.

There is an optimal length of time for each run which is approximately $T = K\sqrt{T_L T_C}$ where $K$ is some constant about 2.0, $T_L$ is the luminosity lifetime which is currently about 20 hours and $T_C$ is the average time to recycle from dump to stable beams. The recycle time can be as short as 2.5 hours but the average will be longer and unpredictable due to unexpected problems.

So one 18 hour run is better than two 9 hour runs, but anything longer than 18 hours is probably inefficient.

As a general rule they may run until the luminosity is about half the peak, but this does not take into account the recycle times.

• Luboš Motl says:

The disease of being obsessed by watching LHC status a few times a day is called “intelligence”.

It’s similar to the sexual deviation in which a man likes attractive 17-year-old girls: this deviation is called “heterosexuality”. ;-)

• carla says:

@Lubos, well as I type, they’re filliing for 624 bunches which means another luminosity record and me hoping for the next 18 hours they can get the integrated luminosity to over 30/pb for another record.

We’re getting close to the magic 350/pb and testing of the Indian Super Symmetric Island, eh Lubos? ;)

• carla says:

Aaaaaah, the beams are back, at long last. Now the men in white coats can leave me in peace…

• Bill K says:

1200 bunches today, Carla!

• carla says:

@Bill 1200? phft 1308 bunches for over an hour!

3. socratus says:

=== .
In 1906, Rutherford studied internal structure of atoms,
bombarding them with high energy a- particles.
This idea helped him understand the structure of atom.
But the clever Devil interfered and gave advice to physicists
to enlarge the target. Bomb them!
And physicist created huge cannon-accelerators of particles.
And they began to bomb micro particles in the vacuum, in hoping
to understand their inner structure. And they were surprised with
the results of this bombing. Several hundreds of completely new
strange particles appeared. They lived a very little time and do not
relate to our world. Our Earth needs its real constants of nature.
But this was forgotten.
What God carefully created, is destroyed in accelerators.
And they are proud of that. They say: we study the inner structure
of the particles. The clever and artful Devil is glad. He again has deceived man.
Physicist think, that an accelerator – is first of all the presence of huge energy.
And the Devil laughs. He knows, that an accelerator – is first of all the Vacuum.
But this, he has withheld from man.
He has not explained that the Vacuum is infinite and inexhaustible.
And in infinity there is contained an infinite variety of particles.
And by bombing the vacuum, one can find centaurs and sphinxes.
But my God, save us from their presence on Earth.
========= .. ========.
Rutherford was right.
His followers are mistaken.
Why?
Imagine, that I want to plant a small apple- tree.
For this purpose I shall dig out a hole of 1 meter width and 1,20 m depth.
It is normal.
But if to plant a small apple- tree, I shall begin to dig
a base for a huge building (skyscraper),
or if to begin drill ground with 10 km. depth,
will you call me a normal man?
========== .. ===============.
Imagine a man who breaks watches on the wall.
And then he tries to understand the mechanism of the watches
by thrown cogwheels, springs and small screws.
Does he have many chances to succeed?
As many as the scientists have who aspire to understand
the inner structure of electron by breaking them into accelerators.
If not take into account the initial conditions of Genesis,
the fantasies of the scientists may be unlimited.
========== . ======== .
The Nature works very economical.
For example, biologists know 100 ( hundred ) kinds of
amino acids. But only 20 ( twenty) kinds of amino acids
are suitable to produce molecules of protein, from which all
different cells created on our planet. What are about another
80 % of amino acids? They are dead end of evolution.
The physicists found many ( 1000 ) new elementary particles in
accelerators. But we need only one ( 1) electron and one (1 )
proton to create first atom, to begin to create the Nature.
All another elementary particles (mesons, muons , bosons, taus,
all their girlfriends – antiparticles, all quarks and antiquarks…etc)
============.
What was before – “ the big bang” or the vacuum ?
The physicists created “ Europe’s Large Hadron Colider “
They made the vacuum and after they generated a big reaction
between two colliding particles in some small imitation of the
“big bang”. They didn’t make this process in the reverse.
So, what was prior in the Universe: “ big bang” or vacuum?
===========================..
The Universe as a whole is Vacuum, first of all.
=== .
Best wishes.
=========================.

4. carla says:

It’s interesting seeing how you might get a few days of great runs and then a bad run with problems that seem to be unrelated.

late yesterday evening there was beam loss, early in the morning there was a cryo problem, afternoon there was some problem with beam focusing, evening another cryo problem.

Did the cryo stuff fall off the back of a lorry? ;)

• Philip Gibbs says:

Yes, the problems do seem to come in batches. It makes it hard to predict how much data they will collect over the year.

Actually the working of the cryo is considered to be very good overall.
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