Showing 25 of 103 results

#### Measurement of the nuclear modification factor for inclusive jets in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV with the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
2018.
Inspire Record 1673184

Measurements of the yield and nuclear modification factor, $R_\mathrm{ AA}$, for inclusive jet production are performed using 0.49 nb$^{-1}$ of Pb+Pb data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV and 25 pb$^{-1}$ of $pp$ data at $\sqrt{s}=5.02$ TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-$k_t$ algorithm with radius parameter $R=0.4$ and are measured over the transverse momentum range of 40-1000 GeV in six rapidity intervals covering $|y|<2.8$. The magnitude of $R_\mathrm{ AA}$ increases with increasing jet transverse momentum, reaching a value of approximately 0.6 at 1 TeV in the most central collisions. The magnitude of $R_\mathrm{ AA}$ also increases towards peripheral collisions. The value of $R_\mathrm{ AA}$ is independent of rapidity at low jet transverse momenta, but it is observed to decrease with increasing rapidity at high transverse momenta.

35 data tables

The ⟨TAA⟩ and ⟨Npart⟩ values and their uncertainties in each centrality bin.

No description provided.

No description provided.

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#### rivet Analysis Measurement of the cross section for isolated-photon plus jet production in $pp$ collisions at $\sqrt s=13$ TeV using the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Phys.Lett. B780 (2018) 578-602, 2018.
Inspire Record 1645627

The dynamics of isolated-photon production in association with a jet in proton–proton collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb −1 . Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti- kt algorithm with radius parameter R=0.4 and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system. Tree-level plus parton-shower predictions from Sherpa and Pythia as well as next-to-leading-order QCD predictions from Jetphox and Sherpa are compared to the measurements.

5 data tables

Measured cross sections for isolated-photon plus jet production as a function of $E_{\rm T}^{\gamma}$.

Measured cross sections for isolated-photon plus jet production as a function of $p_{\rm T}^{\rm jet-lead}$.

Measured cross sections for isolated-photon plus jet production as a function of $\Delta\phi^{\rm \gamma-jet\ lead}$.

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#### Search for dark matter and other new phenomena in events with an energetic jet and large missing transverse momentum using the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
2017.
Inspire Record 1635274

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton--proton collision data corresponding to an integrated luminosity of 36.1 fb${}^{-1}$ at a centre-of-mass energy of 13 TeV collected in 2015 and 2016 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons ($e$ or $\mu$). Several signal regions are considered with increasing requirements on the missing transverse momentum above 250 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, and supersymmetric particles in several compressed scenarios.

33 data tables

The measured leading jet $p_{T}$ distribution in the W($\rightarrow \mu \nu$)+jets control region, for the $E_{T}^{miss}$ > 250GeV inclusive selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit. The last bin of the distribution contains overflows.

The measured $E_{T}^{miss}$ distribution in the W($\rightarrow e \nu$)+jets control region, for the $E_{T}^{miss}$ > 250GeV inclusive selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit. The last bin of the distribution contains overflows.

The measured leading jet $p_{T}$ distribution in the W($\rightarrow e \nu$)+jets control region, for the $E_{T}^{miss}$ > 250GeV inclusive selection, compared to the background predictions. The latter include the global normalization factors extracted from the fit. The last bin of the distribution contains overflows.

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#### rivet Analysis Measurement of differential cross sections of isolated-photon plus heavy-flavour jet production in pp collisions at $\sqrt{s}=8$ TeV using the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
2017.
Inspire Record 1632756

This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton--proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb$^{-1}$. The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: $|\eta^\gamma|<1.37$ and $1.56<|\eta^\gamma|<2.37$. The measurement covers photon transverse energies $25<E_\textrm{T}^\gamma<400$ GeV and $25<E_\textrm{T}^\gamma<350$ GeV respectively for the two $|\eta^\gamma|$ regions. For each jet flavour, the ratio of the cross sections in the two $|\eta^\gamma|$ regions is also measured. The measurement is corrected for detector effects and compared to leading-order and next-to-leading-order perturbative QCD calculations, based on various treatments and assumptions about the heavy-flavour content of the proton. Overall, the predictions agree well with the measurement, but some deviations are observed at high photon transverse energies. The total uncertainty in the measurement ranges between 13% and 66%, while the central $\gamma+b$ measurement exhibits the smallest uncertainty, ranging from 13% to 27%, which is comparable to the precision of the theoretical predictions.

12 data tables

Measured fiducial integrated $\gamma+b$ and $\gamma+c$ cross sections for $|\eta^\gamma|<1.37$ and $1.56<|\eta^\gamma|<2.37$.

Measured $\gamma+b$ fiducial differential cross section as a function of $E_\text{T}^\gamma$ for $|\eta^\gamma|<1.37$.

Measured $\gamma+b$ fiducial differential cross section as a function of $E_\text{T}^\gamma$ for $1.56<|\eta^\gamma|<2.37$.

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#### Measurement of jet fragmentation in Pb+Pb and $pp$ collisions at $\sqrt{s_\mathrm{NN}} = 2.76$ TeV with the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
2017.
Inspire Record 1511869

The distributions of transverse momentum and longitudinal momentum fraction of charged particles in jets are measured in Pb+Pb and pp collisions with the ATLAS detector at the LHC. The distributions are measured as a function of jet transverse momentum and rapidity. The analysis utilises an integrated luminosity of 0.14 nb$^{-1}$ of Pb+Pb data and 4.0 pb$^{-1}$ of pp data collected in 2011 and 2013, respectively, at the same centre-of-mass energy of 2.76 TeV per colliding nucleon pair. The distributions measured in pp collisions are used as a reference for those measured in Pb+Pb collisions in order to evaluate the impact on the internal structure of jets from the jet energy loss of fast partons propagating through the hot, dense medium created in heavy-ion collisions. Modest but significant centrality-dependent modifications of fragmentation functions in Pb+Pb collisions with respect to those in pp collisions are seen. No significant dependence of modifications on jet $p_{\mathrm{T}}$ and rapidity selections is observed except for the fragments with the highest transverse momenta for which some reduction of yields is observed for more forward jets.

81 data tables

D(pt) distributions for pp and Pb+Pb collisions, jet rapidity |y| < 2.1.

D(pt) distributions for pp and Pb+Pb collisions, jet rapidity |y| < 0.3.

D(pt) distributions for pp and Pb+Pb collisions, jet rapidity 0.3 < |y| < 0.8.

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#### High-$E_{\rm T}$ isolated-photon plus jets production in $pp$ collisions at $\sqrt s=$ 8 TeV with the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
Nucl.Phys. B918 (2017) 257-316, 2017.
Inspire Record 1499475

The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 20.2 fb−1 . Measurements of isolated-photon plus jets cross sections are presented as functions of the photon and jet transverse momenta. The cross sections as functions of the azimuthal angle between the photon and the jets, the azimuthal angle between the jets, the photon–jet invariant mass and the scattering angle in the photon–jet centre-of-mass system are presented. The pattern of QCD radiation around the photon and the leading jet is investigated by measuring jet production in an annular region centred on each object; enhancements are observed around the leading jet with respect to the photon in the directions towards the beams. The experimental measurements are compared to several different theoretical calculations, and overall a good description of the data is found.

35 data tables

Measured cross sections for isolated-photon plus 1jet production as a function of $E_{\rm T}^{\gamma}$.

Measured cross sections for isolated-photon plus 1jet production as a function of $p_{\rm T}^{\rm jet1}$.

Measured cross sections for isolated-photon plus 1jet production as a function of $m^{\gamma-\rm jet1}$.

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#### rivet Analysis Measurement of $W$ boson angular distributions in events with high transverse momentum jets at $\sqrt{s}=$ 8 TeV using the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
2016.
Inspire Record 1487726

The $W$ boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton--proton collisions at a centre-of-mass energy $\sqrt{s}=$ 8 TeV at the Large Hadron Collider, corresponding to an integrated luminosity of 20.3 fb$^{-1}$. The focus is on the contributions to $W$ + jets processes from real $W$ emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic $W$ decay.

5 data tables

Measured integrated cross-sections as a function of leading jet transverse momentum for the collinear region ($0.2 < \Delta R < 2.4$), the back-to-back region ($\Delta R > 2.4$) and inclusively.

Measured cross-section as a function of angular separation between the muon and the closest jet. Multiplicative correction factors for using prompt muons and prompt dressing photons in the particle-level selection, derived from ALPGEN 2.14 interfaced with PYTHIA 6.426, are also shown.

Breakdown of uncertainties in percent.

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#### rivet Analysis rivet Analysis Study of hard double-parton scattering in four-jet events in pp collisions at $\sqrt{s}=7$ TeV with the ATLAS experiment

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
JHEP 1611 (2016) 110, 2016.
Inspire Record 1479760
21 data tables

Normalized distribution of the variable $\Delta^{p_{\mathrm{T}}}_{34}$, defined in Eq (16) of the paper, in data after unfolding to particle level.

Normalized distribution of the variable $\Delta\phi_{34}$, defined in Eq (16) of the paper, in data after unfolding to particle level.

Normalized distribution of the variable $\Delta^{p_{\mathrm{T}}}_{12}$, defined in Eq (16) of the paper, in data after unfolding to particle level.

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#### Measurement of the $b\overline{b}$ dijet cross section in $pp$ collisions at $\sqrt{s} = 7$ TeV with the ATLAS detector

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
2016.
Inspire Record 1478355

The dijet production cross section for jets containing a $b$-hadron ($b$-jets) has been measured in proton-proton collisions with a centre-of-mass energy of $\sqrt{s} = 7$ TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of 4.2 fb$^{-1}$. The cross section is measured for events with two identified $b$-jets with a transverse momentum $p_T > 20$ GeV and a minimum separation in the $\eta$-$\phi$ plane of $\Delta R = 0.4$. At least one of the jets in the event is required to have $p_T > 270$ GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the $b$-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization.

6 data tables

Results for the m_bb distribution. Statistical and systematic uncertainties are quoted.

Results for the DeltaPhi distribution. Statistical and systematic uncertainties are quoted.

Results for the y* distribution. Statistical and systematic uncertainties are quoted.

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#### Search for scalar leptoquarks in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS experiment

The collaboration Aaboud, Morad ; Aad, Georges ; Abbott, Brad ; et al.
New J.Phys. 18 (2016) 093016, 2016.
Inspire Record 1462258
4 data tables

Normalisation factors for the main backgrounds obtained from the combined fit in each of the channels. The total uncertainty is given.

Search for the first generation leptoquarks (LQs). Event yields in the Z control region (CR), ttbar CR and in the signal region (SR). Each CR is treated as one bin in the profile likelihood fit. The SR is split to 7 bins according to $m_{\text{LQ}}^{\text{min}}$ for the fit. The table below shows the total number of events in each CR. For the SR, it shows the number of events per 100 GeV as a function of $m_{\text{LQ}}^{\text{min}}$. The background expectations are scaled by a scale factor extracted from the fit. However, the uncertainties shown are the pre-fit ones. The data event yield uncertainty is statistical (gaussian). The background uncertainty consists of all the experimental and theoretical components summed in quadrature. The uncertainty of the fit-extracted background scale factor is also added in quadrature.

Search for the second generation leptoquarks (LQs). Event yields in the Z control region (CR), ttbar CR and in the signal region (SR). Each CR is treated as one bin in the profile likelihood fit. The SR is split to 7 bins according to $m_{\text{LQ}}^{\text{min}}$ for the fit. The table below shows the total number of events in each CR. For the SR, it shows the number of events per 100 GeV as a function of $m_{\text{LQ}}^{\text{min}}$. The background expectations are scaled by a scale factor extracted from the fit. However, the uncertainties shown are the pre-fit ones. The data event yield uncertainty is statistical (gaussian). The background uncertainty consists of all the experimental and theoretical components summed in quadrature. The uncertainty of the fit-extracted background scale factor is also added in quadrature.

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#### Measurement of the dependence of transverse energy production at large pseudorapidity on the hard-scattering kinematics of proton-proton collisions at $\sqrt{s} = 2.76$ TeV with ATLAS

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Lett. B756 (2016) 10-28, 2016.
Inspire Record 1407478
34 data tables

Mean value of the sum of the transverse energy in -4.9 < eta < -3.2 in pp collisions, <SumET>. Reported as a function of dijet pT^avg, shown here for +2.1 < eta^dijet < +2.8.

Mean value of the sum of the transverse energy in -4.9 < eta < -3.2 in pp collisions, <SumET>. Reported as a function of dijet pT^avg, shown here for +1.2 < eta^dijet < +2.1.

Mean value of the sum of the transverse energy in -4.9 < eta < -3.2 in pp collisions, <SumET>. Reported as a function of dijet pT^avg, shown here for +0.8 < eta^dijet < +1.2.

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#### Dijet production in $\sqrt{s}=$ 7 TeV $pp$ collisions with large rapidity gaps at the ATLAS experiment

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Lett. B754 (2016) 214-234, 2016.
Inspire Record 1402356

A $6.8 \ {\rm nb^{-1}}$ sample of $pp$ collision data collected under low-luminosity conditions at $\sqrt{s} = 7$ TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with $p_\mathrm{T} > 20$ GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in $\Delta\eta^F$, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, $\tilde{\xi}$, of the fractional momentum loss of the proton assuming single diffractive dissociation ($pp \rightarrow pX$). Model comparisons indicate a dominant non-diffractive contribution up to moderately large $\Delta\eta^F$ and small $\tilde{\xi}$, with a diffractive contribution which is significant at the highest $\Delta\eta^F$ and the lowest $\tilde{\xi}$. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions.

6 data tables

The cross section differential in the forward rapidity gap size, DELTA(C=RAPGAP), for events with at least two jets of pt > 20 GeV found by the anti-kt jet algorithm with R=0.6.

The cross section differential in the forward rapidity gap size, DELTA(C=RAPGAP), for events with at least two jets of pt > 20 GeV found by the anti-kt jet algorithm with R=0.4.

The cross section differential in the fraction of the proton four-momentum carried by the Pomeron, LOG10(C=XI), for events with at least two jets of pt > 20 GeV found by the anti-kt jet algorithm with R=0.6.

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#### rivet Analysis Measurement of four-jet differential cross sections in $\sqrt{s}=8$ TeV proton-proton collisions using the ATLAS detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
JHEP 1512 (2015) 105, 2015.
Inspire Record 1394679

Differential cross sections for the production of at least four jets have been measured in proton-proton collisions at $\sqrt{s}=8$ TeV at the Large Hadron Collider using the ATLAS detector. Events are selected if the four anti-k$_{t}$ R = 0.4 jets with the largest transverse momentum (p$_{T}$) within the rapidity range |y| < 2.8 are well separated (ΔR$_{4j}^{min}$  > 0.65), all have p$_{T}$ > 64 GeV, and include at least one jet with p$_{T}$ > 100 GeV. The dataset corresponds to an integrated luminosity of 20.3 fb$^{−}^{1}$ . The cross sections, corrected for detector effects, are compared to leading-order and next-to-leading-order calculations as a function of the jet momenta, invariant masses, minimum and maximum opening angles and other kinematic variables.

46 data tables

Measured differential four-jet cross section for R=0.4 jets, in bins of pT1, along with the uncertainties in the measurement. The events are selected using the inclusive analysis cuts. All uncertainties are given in %. The first uncertainty quoted is due to the number of data events. DSYS:mcstat is the statistical uncertainty due to the number of MC simulation events. The other columns, denoted with DSYS, correspond to the experimental systematic uncertainties arising from JES, JER, unfolding and luminosity, respectively.

Measured differential four-jet cross section for R=0.4 jets, in bins of pT2, along with the uncertainties in the measurement. The events are selected using the inclusive analysis cuts. All other details are as for pT1.

Measured differential four-jet cross section for R=0.4 jets, in bins of pT3, along with the uncertainties in the measurement. The events are selected using the inclusive analysis cuts. All other details are as for pT1.

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#### rivet Analysis Measurements of fiducial cross-sections for $t\bar{t}$ production with one or two additional b-jets in pp collisions at $\sqrt{s}$ =8 TeV using the ATLAS detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Eur.Phys.J. C76 (2016) 11, 2016.
Inspire Record 1390114

Fiducial cross-sections for $t\bar{t}$ production with one or two additional b-jets are reported, using an integrated luminosity of 20.3 fb$^{-1}$ of proton–proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for $t\bar{t}$ events with at least one additional b-jet is measured to be 950 $\pm$ 70 (stat.)$^{+240-190}$  (syst.) fb in the lepton-plus-jets channel and 50 $\pm$ 10 (stat.)$^{+15-10}$  (syst.) fb in the $e \mu$ channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 $\pm$ 3.5 (stat.) $\pm$ 5.7 (syst.) fb in the dilepton channel ( $e \mu$ ,  $\mu \mu$ , and  ee) using a method based on tight selection criteria, and 13.5 $\pm$ 3.3 (stat.)  $\pm$ 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 $\pm$ 0.33 (stat.) $\pm$ 0.28 (syst.)% for the ratio of $t\bar{t}$ production with two additional b-jets to $t\bar{t}$ production with any two additional jets. All measurements are in good agreement with recent theory predictions.

8 data tables

Measured fiducial cross section for $t\bar{t}$ events with exactly one lepton and at least five jets, of which at least three are b-jets. The definition of the cross-section includes $t\bar{t}+Z / H$ events that pass the fiducial requirements.

Measured fiducial cross section for $t\bar{t}$ events with two leptons and at least three b-jets. The definition of the cross-section includes $t\bar{t}+Z / H$ events that pass the fiducial requirements.

Measured fiducial cross section for $t\bar{t}$ events with two leptons and at least four b-jets. The definition of the cross-section includes $t\bar{t}+Z / H$ events that pass the fiducial requirements.

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#### rivet Analysis Measurement of transverse energy-energy correlations in multi-jet events in $pp$ collisions at $\sqrt{s} = 7$ TeV using the ATLAS detector and determination of the strong coupling constant $\alpha_{\mathrm{s}}(m_Z)$

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Lett. B750 (2015) 427-447, 2015.
Inspire Record 1387176
3 data tables

Values of the transverse energy-energy correlation function (TEEC).

Values of the asymmetry on the transverse energy-energy correlation function (ATEEC).

Values of the non-perturbative correction factors for the TEEC function derived using Pythia 6 AUET2B.

#### Search for New Phenomena in Dijet Angular Distributions in Proton-Proton Collisions at $\sqrt{s} = 8$ TeV Measured with the ATLAS Detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Rev.Lett. 114 (2015) 221802, 2015.
Inspire Record 1357594

A search for new phenomena in LHC proton-proton collisions at a center-of-mass energy of s=8  TeV was performed with the ATLAS detector using an integrated luminosity of 17.3  fb−1. The angular distributions are studied in events with at least two jets; the highest dijet mass observed is 5.5 TeV. All angular distributions are consistent with the predictions of the standard model. In a benchmark model of quark contact interactions, a compositeness scale below 8.1 TeV in a destructive interference scenario and 12.0 TeV in a constructive interference scenario is excluded at 95% C.L.; median expected limits are 8.9 TeV for the destructive interference scenario and 14.1 TeV for the constructive interference scenario.

7 data tables

mjj region 600 - 800 GeV. The observed systematic is the experimental uncertainty, while the SM prediction systematic is the theoretical uncertainty.

mjj region 800 - 1200 GeV. The observed systematic is the experimental uncertainty, while the SM prediction systematic is the theoretical uncertainty.

mjj region 1200 - 1600 GeV. The observed systematic is the experimental uncertainty, while the SM prediction systematic is the theoretical uncertainty.

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#### Search for low-scale gravity signatures in multi-jet final states with the ATLAS detector at $\sqrt{s} = 8$ TeV

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
JHEP 1507 (2015) 032, 2015.
Inspire Record 1357199

We search for evidence of physics beyond the Standard Model in the production of final states with multiple high transverse momentum jets, using 20.3 fb$^{-1}$ of proton-proton collision data recorded by the ATLAS detector at $\sqrt{s} = 8$ TeV. No excess of events beyond Standard Model expectations is observed, and upper limits on the visible cross-section for non-Standard Model production of multi-jet final states are set. Using a wide variety of models for black hole and string ball production and decay, the limit on the cross-section times acceptance is as low as 0.16 fb at the 95% CL for a minimum scalar sum of jet transverse momentum in the event of about 4.3 TeV. Using models for black hole and string ball production and decay, exclusion contours are determined as a function of the production mass threshold and the gravity scale. These limits can be interpreted in terms of lower-mass limits on black hole and string ball production that range from 4.6 to 6.2 TeV.

13 data tables

Number of data events (20.3 fb$^{-1}$), number of predicted events from the fit, statistical uncertainty on the fit, systematic uncertainty on the choice of control region, and on the choice of fit function versus inclusive $H_{\textrm{T}}^{\textrm{min}}$ lower bin edge for inclusive jet multiplicity $N_{\textrm{Jet}} \geq 3$. The total uncertainty is obtained by adding the three uncertainties linearly.

Number of data events (20.3 fb$^{-1}$), number of predicted events from the fit, statistical uncertainty on the fit, systematic uncertainty on the choice of control region, and on the choice of fit function versus inclusive $H_{\textrm{T}}^{\textrm{min}}$ lower bin edge for inclusive jet multiplicity $N_{\textrm{Jet}} \geq 4$. The total uncertainty is obtained by adding the three uncertainties linearly.

Number of data events (20.3 fb$^{-1}$), number of predicted events from the fit, statistical uncertainty on the fit, systematic uncertainty on the choice of control region, and on the choice of fit function versus inclusive $H_{\textrm{T}}^{\textrm{min}}$ lower bin edge for inclusive jet multiplicity $N_{\textrm{Jet}} \geq 5$. The total uncertainty is obtained by adding the three uncertainties linearly.

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#### Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at $\sqrt{s}=$8 TeV with the ATLAS detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Eur.Phys.J. C75 (2015) 299, 2015.
Inspire Record 1343107

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb ${}^{-1}$ of $\sqrt{s}=8$  TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with $p_{\mathrm {T}}> 120$  GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between $E_{\mathrm {T}}^{\mathrm {miss}}>150$  GeV and $E_{\mathrm {T}}^{\mathrm {miss}}> 700$  GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.

45 data tables

Distributions of the measured transverse mass distribution of the identified muon in the $W\mu\nu$+jets control region for the inclusive SR1 selection, compared to the background expectations. The latter include the global normalization factors extracted from the data. Where appropriate, the last bin of the distribution includes overflows.

Measured $E_{T}^{miss}$ distribution in the $W\mu\nu$+jets control region for the inclusive SR1 selection, compared to the background expectations. The latter include the global normalization factors extracted from the data. Where appropriate, the last bin of the distribution includes overflows.

Measured leading jet $p_{T}$ distribution in the $W\mu\nu$+jets control region for the inclusive SR1 selection, compared to the background expectations. The latter include the global normalization factors extracted from the data. Where appropriate, the last bin of the distribution includes overflows.

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#### Centrality and rapidity dependence of inclusive jet production in $\sqrt{s_\mathrm{NN}} = 5.02$ TeV proton-lead collisions with the ATLAS detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Lett. B748 (2015) 392-413, 2015.
Inspire Record 1334140

Measurements of the centrality and rapidity dependence of inclusive jet production in sNN=5.02 TeV proton–lead ( p+Pb ) collisions and the jet cross-section in s=2.76 TeV proton–proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb −1 and 4.0 pb −1 , respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval −4.9<η<−3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum ( pT ) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a pT -dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all pT at forward rapidities and for large pT at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton–nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton–parton kinematics.

171 data tables

The $R_{\mathrm{coll}}$ and $T_{p\mathrm{A}}$ values and their uncertainties in each centrality bin.

Per-event jet yields in 0-90% p+Pb collisions, within the centre of mass rapidity -2.1 to -1.2 (positive denotes downstream proton direction).

Per-event jet yields in 0-90% p+Pb collisions, within the centre of mass rapidity -1.2 to -0.8 (positive denotes downstream proton direction).

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#### Measurements of the Nuclear Modification Factor for Jets in Pb+Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV with the ATLAS Detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Phys.Rev.Lett. 114 (2015) 072302, 2015.
Inspire Record 1326911

<p>Measurements of inclusive jet production are performed in <inline-formula><mml:math display="inline"><mml:mi>p</mml:mi><mml:mi>p</mml:mi></mml:math></inline-formula> and <inline-formula><mml:math display="inline"><mml:mi>Pb</mml:mi><mml:mo>+</mml:mo><mml:mi>Pb</mml:mi></mml:math></inline-formula> collisions at <inline-formula><mml:math display="inline"><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mi>NN</mml:mi></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>2.76</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:math></inline-formula> with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and <inline-formula><mml:math display="inline"><mml:mrow><mml:mn>0.14</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi>nb</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula>, respectively. The jets are identified with the anti-<inline-formula><mml:math display="inline"><mml:msub><mml:mi>k</mml:mi><mml:mi>t</mml:mi></mml:msub></mml:math></inline-formula> algorithm with <inline-formula><mml:math display="inline"><mml:mi>R</mml:mi><mml:mo>=</mml:mo><mml:mn>0.4</mml:mn></mml:math></inline-formula>, and the spectra are measured over the kinematic range of jet transverse momentum <inline-formula><mml:math display="inline"><mml:mn>32</mml:mn><mml:mo>&lt;</mml:mo><mml:msub><mml:mi>p</mml:mi><mml:mi mathvariant="normal">T</mml:mi></mml:msub><mml:mo>&lt;</mml:mo><mml:mn>500</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi></mml:math></inline-formula> and absolute rapidity <inline-formula><mml:math display="inline"><mml:mo stretchy="false">|</mml:mo><mml:mi>y</mml:mi><mml:mo stretchy="false">|</mml:mo><mml:mo>&lt;</mml:mo><mml:mn>2.1</mml:mn></mml:math></inline-formula> and as a function of collision centrality. The nuclear modification factor <inline-formula><mml:math display="inline"><mml:msub><mml:mi>R</mml:mi><mml:mi>AA</mml:mi></mml:msub></mml:math></inline-formula> is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to <inline-formula><mml:math display="inline"><mml:mi>p</mml:mi><mml:mi>p</mml:mi></mml:math></inline-formula> collisions. The <inline-formula><mml:math display="inline"><mml:msub><mml:mi>R</mml:mi><mml:mi>AA</mml:mi></mml:msub></mml:math></inline-formula> shows a slight increase with <inline-formula><mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>p</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">T</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> and no significant variation with rapidity.</p>

46 data tables

The $\langle T_{\mathrm{AA}} \rangle$ and $\langle N_{\mathrm{part}} \rangle$ values and their uncertainties in each centrality bin.

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#### rivet Analysis Measurement of three-jet production cross-sections in $pp$ collisions at 7 TeV centre-of-mass energy using the ATLAS detector

The collaboration Aad, Georges ; Abbott, Brad ; Abdallah, Jalal ; et al.
Eur.Phys.J. C75 (2015) 228, 2015.
Inspire Record 1326641

Double-differential three-jet production cross-sections are measured in proton–proton collisions at a centre-of-mass energy of $\sqrt{s} = 7\mathrm \,TeV{}$ using the ATLAS detector at the large hadron collider. The measurements are presented as a function of the three-jet mass $(m_{jjj})$ , in bins of the sum of the absolute rapidity separations between the three leading jets $(\left| Y^{*}\right| )$ . Invariant masses extending up to 5  TeV are reached for $8< \left| Y^{*}\right| < 10$ . These measurements use a sample of data recorded using the ATLAS detector in 2011, which corresponds to an integrated luminosity of $4.51~\text{ fb }^{-1}$ . Jets are identified using the anti- $k_{t}$ algorithm with two different jet radius parameters, $R=0.4$ and $R=0.6$ . The dominant uncertainty in these measurements comes from the jet energy scale. Next-to-leading-order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. Good agreement is found between the data and the theoretical predictions based on most of the available sets of parton distribution functions, over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values.

10 data tables

Measured three-jet double-differential cross sections as a function of M(3JET) in |Y*|<2 for anti-kt R=0.4 jets. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.

Measured three-jet double-differential cross sections as a function of M(3JET) in 2<=|Y*|<4 for anti-kt R=0.4 jets. The three columns correspond to nominal, stronger or weaker correlations between jet energy scale uncertainty components.
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