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Plots from Rivet analyses

Invariant cross section of neutral pions at mid-rapidity in $8\,$TeV pp collisions (ALICE_2017_I1620477)

Inspire | HepData | Analysis reference | Eur. Phys. J. C (2018) 78: 263 | 10.1140/epjc/s10052-018-5612-8 | arXiv:hep-ex/1708.08745

Transverse momentum spectra of neutral pions and $\eta$ mesons measured at $0.3<p_T<35 GeV/c$ and $0.5<p_T<35 GeV/c$, respectively, and the ratio $\pi^{0}/\eta$, obtained at mid-rapidity in $pp$ collisions at $\sqrt(s) = 8\,$TeV with ALICE at the LHC.

Invariant cross section of neutral pions measured at mid-rapidity in pp collisions at $2.76\,$TeV. (ALICE_2017_I1512110)

Inspire | HepData | Analysis reference

Transverse momentum spectra of neutral pions and $\eta$ mesons measured at 0.4<p_T<40 GeV/c and 0.6<p_T<20 GeV/c, respectively, and the ratio $\pi^{0}/\eta$, obtained at mid-rapidity in pp collisions at $\sqrt(s) = 2.76\,$TeV with ALICE at the LHC.

Transverse momentum spectra of pions, kaons and protons in $pp$ collisions at 7 TeV (ALICE_2015_I1357424)

Inspire | HepData | Analysis reference

Obtaining the transverse momentum spectra of primary pions, kaons and protons in $pp$ collisions at $\sqrt{s} = 7$ TeV with ALICE at the LHC. K/pi and p/pi ratios are also included.

Production of $\Sigma(1385)^{\pm}$ and $\Xi(1530)^{0}$ in proton-proton collisions at $\sqrt{s} =$ 7 TeV (ALICE_2014_I1300380)

Inspire | HepData | Analysis reference

Transverse momentum spectra $\frac{1}{N_{\rm inel}} \frac{{\rm d}^2N}{{\rm d}p_{\rm T}{\rm d}y}$ of $\Sigma(1385)^{\pm}$, $\overline{\Sigma}(1385)^{\pm}$ and $(\Xi(1530)^{0}+\overline{\Xi}(1530)^{0})/2$ at mid-rapidity ($|y| < 0.5$) in inelastic proton-proton collisions at $\sqrt{s} =$ 7 TeV

Measurement of inelastic, single- and double-diffraction cross sections in proton--proton collisions at the LHC with ALICE (ALICE_2012_I1181770)

Inspire | HepData | Analysis reference | arXiv:1208.4968

Measurements of cross-sections of inelastic and diffractive processes in proton-proton collisions at $\sqrt{s} = 900$, 2760 and 7000 GeV. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions. Single-diffractive events are selected with $M_{X} < 200 \text{GeV}/c^2$ and double-diffractive events defined as NSD events with $\Delta\eta > 3$. To measure the inelastic cross-section, beam properties were determined with van der Meer scans using a simulation of diffraction adjusted to data. Note that these are experimental approximations to theoretical concepts -- it is not totally clear whether the data point values are model-independent. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

pT of neutral pions and $\eta$ mesons in $pp$ collisions at $7\,$TeV and $0.9\,$TeV (ALICE_2012_I1116147)

Inspire | HepData | Analysis reference | Phys.Lett. B717 (2012) 162-172 | doi:10.1016/j.physletb.2012.09.015 | arXiv:1205.5724

Transverse momentum spectra of neutral pions and $\eta$ mesons and the ratio $\pi^0/\eta$, obtained at mid-rapidity in pp collisions at $\sqrt{s} = 7\,$TeV with ALICE at the LHC. The transverse momentum spectrum of neutral pions is also given for $\sqrt{s} = 0.9\,$TeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Measurement of charm production at central rapidity in proton-proton collisions at $\sqrt{s}=7$ TeV (ALICE_2012_I944757)

Inspire | HepData | Analysis reference | doi:10.1007/JHEP01(2012)128 | arXiv:1111.1553

The $p_\text{T}$-differential inclusive production cross sections of the prompt charmed mesons $D^0$, $D^+$, and $D^{\ast +}$ in the rapidity range $|y|<0.5$ were measured in proton-proton collisions at $\sqrt{s}=7$ TeV at the LHC using the ALICE detector. Reconstructing the decays $D^0 \to K^-\pi^+$, $D^+\to K^-\pi^+\pi^+$, $D^{\ast +} \to D^0\pi^+$, and their charge conjugates, about 8,400 $D^0$, 2,900 $D^+$, and 2,600 $D^{\ast +}$ mesons with $1 < p_\text{T} < 24$ GeV/$c$ were counted, after selection cuts, in a data sample of 3.14$\times 10^8$ events collected with a minimum-bias trigger (integrated luminosity $L_\text{int} = 5$/nb). The results are described within uncertainties by predictions based on perturbative QCD.

Transverse momentum spectra of pions, kaons and protons in pp collisions at 0.9 TeV (ALICE_2011_S8945144)

Inspire | HepData | Analysis reference | Eur.Phys.J.C71:1655,2011. | arXiv:1101.4110

Obtaining the transverse momentum spectra of pions, kaons and protons in $pp$ collisions at $\sqrt{s} = 0.9$ TeV with ALICE at the LHC. Mean transverse momentum as a function of the mass of the emitted particle is also included.

Strange particle production in proton-proton collisions at $\sqrt{s} = 0.9$ TeV with ALICE at the LHC. (ALICE_2011_S8909580)

Inspire | HepData | Analysis reference | Eur.Phys.J.C71:1594,2011.

Transverse momentum spectra of strange particles ($K^0_S$, $\Lambda$, $\phi$ and $\Xi$) in $pp$ collisions at $\sqrt{s} = 0.9$ TeV with ALICE at the LHC. The ratio of cross-sections as a function of pT for $\Lambda/K^0_S$ is also included.

Charged particle $\langle p_\perp \rangle$ vs. $N_\text{ch}$ in $pp$ collisions at 900 GeV (ALICE_2010_S8706239)

Inspire | HepData | Analysis reference | Phys.Lett.B693:53-68,2010 | arXiv:1007.0719

ALICE measurement of $\langle p_\perp \rangle$ vs. $N_\text{ch}$ and invariant particle yield (as function of $p_\perp$) in proton-proton collisions at $\sqrt{s} = 900 \text{GeV}$.

Pseudorapidities at three energies, charged multiplicity at 7 TeV (ALICE_2010_S8625980)

Inspire | HepData | Analysis reference | Eur.Phys.J. C68 (2010) 345-354 | arXiv:1004.3514

This is an ALICE publication with pseudorapities for 0.9, 2.36 and $7 \text{TeV}$ and the charged multiplicity at $7 \text{TeV}$. The analysis requires at least on charged particle in the event. Only the INEL distributions are considered here Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

Charged particle multiplicities at 0.9 and 2.36 TeV in three different pseudorapidity intervals (ALICE_2010_S8624100)

Inspire | HepData | Analysis reference | Eur.Phys.J.C68:89-108,2010 | arXiv:1004.3034

This is an ALICE analysis where charged particle multiplicities (including the zero bin) have been measured in three different pseudorapidity intervals ($|\eta|<0.5; |\eta|<1.0; |\eta|<1.3$. Only the INEL distributions have been considered here, i.e. this analysis can only be meaningfully compared to PYTHIA 6 with diffractive processes disabled. The data were taken at 900 and 2360 GeV. Beam energy must be specified as analysis option "ENERGY" when rivet-merging samples.

energy asymmetry in ttj @ 13 TeV (ATLAS_2021_I1941095)

Inspire | HepData | Analysis reference | arXiv:2110.05453

A measurement of the energy asymmetry in jet-associated top-quark pair production is presented using 139 fb$^{-1}$ of data collected by the ATLAS detector at the Large Hadron Collider during $pp$ collisions at $\sqrt{s}=13$ TeV. The observable measures the different probability of top and antitop quarks to have the higher energy as a function of the jet scattering angle with respect to the beam axis. The energy asymmetry is measured in the semileptonic $t\bar{t}$ decay channel, and the hadronically decaying top quark must have transverse momentum above 350 GeV. The results are corrected for detector effects to particle level in three bins of the scattering angle of the associated jet. The measurement agrees with the SM prediction at next-to-leading-order accuracy in quantum chromodynamics in all three bins. In the bin with the largest expected asymmetry, where the jet is emitted perpendicular to the beam, the energy asymmetry is measured to be $-0.043\pm0.020$, in agreement with the SM prediction of $-0.037\pm0.003$. Interpreting this result in the framework of the Standard Model effective field theory (SMEFT), it is shown that the energy asymmetry is sensitive to the top-quark chirality in four-quark operators and is therefore a valuable new observable in global SMEFT fits.

b-fragmentation at 13 TeV (ATLAS_2021_I1913061)

Inspire | HepData | Analysis reference | arXiv:2108.11650

The fragmentation properties of jets containing $b$-hadrons are studied using charged $B$-mesons in 139 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 13$ TeV, recorded with the ATLAS detector at the LHC during the period from 2015 to 2018. The $B$ mesons are reconstructed using the decay of $B^{\pm}$ into $J/\psi K^{\pm}$, with the $J/\psi$ decaying into a pair of muons. Jets are reconstructed using the anti-$k_t$ algorithm with radius parameter $R=0.4$. The measurement determines the longitudinal and transverse momentum profiles of the reconstructed $B$-hadrons with respect to the axes of the jets to which they are geometrically associated. These distributions are measured in intervals of the jet transverse momentum, ranging from 50 GeV to above 100 GeV. The results are corrected for detector effects and compared with several Monte Carlo predictions using different parton shower and hadronisation models. The results for the longitudinal and transverse profiles provide useful inputs to improve the description of heavy-flavour fragmentation in jets.

Hadronic event shapes in multijet final states (ATLAS_2020_I1808726)

Inspire | HepData | Analysis reference | ATLAS-STDM-2019-02 | arXiv:2007.12600

A measurement of event-shape variables in proton-proton collisions at large momentum transfer is presented using data collected at $\sqrt{s}$=13 TeV with the ATLAS detector at the Large Hadron Collider. Six event-shape variables calculated using hadronic jets are studied in inclusive multijet events using data corresponding to an integrated luminosity of 139 fb$^{-1}$. Measurements are performed in bins of jet multiplicity and in different ranges of the scalar sum of the transverse momenta of the two leading jets, reaching scales beyond 2 TeV. These measurements are compared with predictions from Monte Carlo event generators containing leading-order or next-to-leading order matrix elements matched to parton showers simulated to leading-logarithm accuracy. At low jet multiplicities, shape discrepancies between the measurements and the Monte Carlo predictions are observed. At high jet multiplicities, the shapes are better described but discrepancies in the normalisation are observed.

Top-quark pair single- and double-differential cross-sections in the all-hadronic channel (ATLAS_2020_I1801434)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2018-18 | JHEP 01 (2021) 033 | arXiv:2006.09274

Differential cross-sections are measured for top-quark pair production in the all-hadronic decay mode, using proton-proton collision events collected by the ATLAS experiment in which all six decay jets are separately resolved. Absolute and normalised single- and double-differential cross-sections are measured at particle and parton level as a function of various kinematic variables. Emphasis is placed on well-measured observables in fully reconstructed final states, as well as on the study of correlations between the top-quark pair system and additional jet radiation identified in the event. The study is performed using data from proton-proton collisions at $\sqrt{s} = 13$ TeV collected by the ATLAS detector at the CERN Large Hadron Collider in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb$^{-1}$. The rapidities of the individual top quarks and of the top-quark pair are well modelled by several independent event generators. Significant mismodelling is observed in the transverse momenta of the leading three jet emissions, while the leading top-quark transverse momentum and top-quark pair transverse momentum are both found to be incompatible with several theoretical predictions

Lund jet plane with charged particles (ATLAS_2020_I1790256)

Inspire | HepData | Analysis reference | arXiv:2004.03540

The prevalence of hadronic jets at the LHC requires that a deep understanding of jet formation and structure is achieved in order to reach the highest levels of experimental and theoretical precision. There have been many measurements of jet substructure at the LHC and previous colliders, but the targeted observables mix physical effects from various origins. Based on a recent proposal to factorize physical effects, this Letter presents a double-differential cross-section measurement of the Lund jet plane using 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV proton-proton collision data collected with the ATLAS detector using jets with transverse momentum above 675 GeV. The measurement uses charged particles to achieve a fine angular resolution and is corrected for acceptance and detector effects. Several parton shower Monte Carlo models are compared with the data. No single model is found to be in agreement with the measured data across the entire plane.

Soft-drop observables (ATLAS_2019_I1772062)

Inspire | HepData | Analysis reference | ATLAS-STDM-2017-33 | arXiv:1912.09837

Jet substructure quantities are measured using jets groomed with the soft-drop grooming procedure in dijet events from 32.9 fb$^{-1}$ of $pp$ collisions collected with the ATLAS detector at $\sqrt{s} = 13$ TeV. These observables are sensitive to a wide range of QCD phenomena. Some observables, such as the jet mass and opening angle between the two subjets which pass the soft-drop condition, can be described by a high-order (resummed) series in the strong coupling constant $\alpha_s$. Other observables, such as the momentum sharing between the two subjets, are nearly independent of $\alpha_s$. These observables can be constructed using all interacting particles or using only charged particles reconstructed in the inner tracking detectors. Track-based versions of these observables are not collinear safe, but are measured more precisely, and universal nonperturbative functions can absorb the collinear singularities. The unfolded data are directly compared with QCD calculations and hadron-level Monte Carlo simulations. The measurements are performed in different pseudorapidity regions, which are then used to extract quark and gluon jet shapes using the predicted quark and gluon fractions in each region. All of the parton shower and analytical calculations provide an excellent description of the data in most regions of phase space.

Differential single diffractive cross sections at 8 TeV (ATLAS_2019_I1762584)

Inspire | HepData | Analysis reference | ATLAS-STDM-2018-01 | arXiv:1911.00453 | JHEP 02 (2020) 042

A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy $\sqrt{s} = 8$ TeV is used to study inclusive single diffractive dissociation, $pp \to X p$. The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system X are measured in the central detector components. The fiducial range of the measurement is $-4.0 < \log_{10} \xi < -1.6$ and $0.016 < |t| < 0.43$ GeV$^{2}$, where $\xi$ is the proton fractional energy loss and $t$ is the squared four-momentum transfer. The total cross section integrated across the fiducial range is $1.59 \pm 0.13$ mb. Cross sections are also measured differentially as functions of $\xi$, $t$, and $\Delta \eta$, a variable that characterises the rapidity gap separating the proton and the system X. The data are consistent with an exponential $t$ dependence, d$\sigma$/d$t \approx e^{Bt}$ with slope parameter $B = 7.65 \pm 0.34$ GeV$^{-2}$. Interpreted in the framework of triple Regge phenomenology, the $\xi$ dependence leads to a pomeron intercept of $\alpha(0) = 1.07 \pm 0.09$.

dileptonic ttbar at 13 TeV (ATLAS_2019_I1759875)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2018-17 | Eur.Phys.J.C 80 (2020) 6, 528

The inclusive top quark pair ($t\bar{t}$) production cross-section $\sigma_{t\bar{t}}$ has been measured in proton-proton collisions at $\sqrt{s}=13$ TeV, using 36.1 fb$^{-1}$ of data collected in 2015-2016 by the ATLAS experiment at the LHC. Using events with an opposite-charge $e\mu$ pair and $b$-tagged jets, the cross-section is measured to be: $\sigma_{t\bar{t}} = 826.4 \pm 3.6$ (stat) $\pm 11.5$ (syst) $\pm 15.7$ (lumi) $\pm 1.9$ (beam) pb, where the uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, the integrated luminosity, and the LHC beam energy, giving a total uncertainty of 2.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. It is used to determine the top quark pole mass via the dependence of the predicted cross-section on $m_t^{\mathrm{pole}}$, giving $m_t^{\mathrm{pole}}=173.1^{+2.0}_{-2.1}$ GeV. It is also combined with measurements at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV to derive ratios and double ratios of $t\bar{t}$ and $Z$ cross-sections at different energies. The same event sample is used to measure absolute and normalised differential cross-sections as functions of single-lepton and dilepton kinematic variables, and the results are compared with predictions from various Monte Carlo event generators.

Semileptonic ttbar at 13 TeV (ATLAS_2019_I1750330)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2018-15 | arXiv:1908.07305

Single- and double-differential cross-section measurements are presented for the production of top-quark pairs, in the lepton + jets channel at particle and parton level. Two topologies, resolved and boosted, are considered and the results are presented as a function of several kinematic variables characterising the top and the system and jet multiplicities. The study was performed using data from $pp$ collisions at centre-of-mass energy of 13 TeV collected in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider (LHC), corresponding to an integrated luminosity of 36 fb$^{-1}$. Due to the large $t\bar{t}$ cross-section at the LHC, such measurements allow a detailed study of the properties of top-quark production and decay, enabling precision tests of several Monte Carlo generators and fixed-order Standard Model predictions. Overall, there is good agreement between the theoretical predictions and the data.

K-short and Lambda production in ttbar events at 7 TeV (ATLAS_2019_I1746286)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2016-05 | Eur.Phys.J. C79 (2019) no.12, 1017 | doi:10.1140/epjc/s10052-019-7512-y | arXiv:1907.10862

Measurements of $K^0_S$ and $\Lambda^0$ production in $t\bar{t}$ final states have been performed. They are based on a data sample with integrated luminosity of 4.6 fb$^{-1}$ from proton-proton collisions at a centre-of-mass energy of 7 TeV, collected in 2011 with the ATLAS detector at the Large Hadron Collider. Neutral strange particles are separated into three classes, depending on whether they are contained in a jet, with or without a $b$-tag, or not associated with a selected jet. The aim is to look for differences in their main kinematic distributions. A comparison of data with several Monte Carlo simulations using different hadronisation and fragmentation schemes, colour reconnection models and different tunes for the underlying event has been made. The production of neutral strange particles in $t\bar{t}$ dileptonic events is found to be well described by current Monte Carlo models for $K^0_S$ ans $\Lambda^0$ production within jets, but not for those produced outside jets.

Jet fragmentation using charged particles (ATLAS_2019_I1740909)

Inspire | HepData | Analysis reference | ATLAS-STDM-2017-16 | arXiv:1906.09254 | Phys.Rev.D 100 (2019) 5, 052011

This paper presents a measurement of quantities related to the formation of jets from high-energy quarks and gluons (fragmentation). Jets with transverse momentum 100 GeV $< p_T <$ 2.5 TeV and pseudorapidity $|\eta|<2.1$ from an integrated luminosity of 33 fb$^{-1}$ of $\sqrt{s}=$13 TeV proton-proton collisions are reconstructed with the ATLAS detector at the Large Hadron Collider. Charged-particle tracks with $p_T >$ 500 MeV and $|\eta|<2.5$ are used to probe the detailed structure of the jet. The fragmentation properties of the more forward and the more central of the two leading jets from each event are studied. The data are unfolded to correct for detector resolution and acceptance effects. Comparisons with parton shower Monte Carlo generators indicate that existing models provide a reasonable description of the data across a wide range of phase space, but there are also significant differences. Furthermore, the data are interpreted in the context of quark- and gluon-initiated jets by exploiting the rapidity dependence of the jet flavor fraction. A first measurement of the charged-particle multiplicity using model-independent jet labels (topic modeling) provides a promising alternative to traditional quark and gluon extractions using input from simulation. The simulations provide a reasonable description of the quark-like data across the jet $p_T$ range presented in this measurement, but the gluon-like data have systematically fewer charged particles than the simulations.

Jet substructure at 13 TeV (ATLAS_2019_I1724098)

Inspire | HepData | Analysis reference | ATLAS-STDM-2017-34 | JHEP 1908 (2019) 033 | doi:10.1007/JHEP08(2019)033 | arXiv:1903.02942

A measurement of jet substructure observables is presented using data collected in 2016 by the ATLAS experiment at the LHC with proton-proton collisions at $\sqrt{s} = 13$ TeV. Large-radius jets groomed with the trimming and soft-drop algorithms are studied. Dedicated event selections are used to study jets produced by light quarks or gluons, and hadronically decaying top quarks and W bosons. The observables measured are sensitive to substructure, and therefore are typically used for tagging large-radius jets from boosted massive particles. These include the energy correlation functions and the $N$-subjettiness variables. The number of subjets and the Les Houches angularity are also considered. The distributions of the substructure variables, corrected for detector effects, are compared to the predictions of various Monte Carlo event generators. They are also compared between the large-radius jets originating from light quarks or gluons, and hadronically decaying top quarks and $W$ bosons.

g \to bb at 13 TeV (ATLAS_2018_I1711114)

Inspire | HepData | Analysis reference | ATLAS-STDM-2017-17 | Phys.Rev. D99 (2019) no.5, 052004 | doi:10.1103/PhysRevD.99.052004 | arXiv:1812.09283

The fragmentation of high-energy gluons at small opening angles is largely unconstrained by present measurements. Gluon splitting to $b$-quark pairs is a unique probe into the properties of gluon fragmentation because identified $b$-tagged jets provide a proxy for the quark daughters of the initial gluon. In this study, key differential distributions related to the $g\to b\bar{b}$ process are measured using 33fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data recorded by the ATLAS experiment at the LHC in 2016. Jets constructed from charged-particle tracks, clustered with the anti-$k_\text{t}$ jet algorithm with radius parameter $R=0.2$, are used to probe angular scales below the $R=0.4$ jet radius. The observables are unfolded to particle level in order to facilitate direct comparisons with predictions from present and future simulations. Multiple significant differences are observed between the data and parton shower Monte Carlo predictions, providing input to improve these predictions of the main source of background events in analyses involving boosted Higgs bosons decaying into $b$-quarks.

Measurement of normalized differential distributions in ttbar+photon production at 13 TeV (ATLAS_2018_I1707015)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2017-14 | arXiv:1812.01697

Differential cross-sections for the production of a top-quark pair in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 36.1 fb^-1, collected by the ATLAS detector at the LHC in 2015 and 2016 at a centre-of-mass energy of 13 TeV. The measurements are performed in single-lepton and dilepton final states in a fiducial volume. Events with exactly one photon, one or two leptons, a channel-dependent minimum number of jets, and at least one b-jet are selected. Neural network algorithms are used to separate the signal from the backgrounds. The differential cross-sections are measured as a function of photon transverse momentum, photon absolute pseudorapidity, and angular distance between the photon and its closest lepton in both channels, as well azimuthal opening angle and absolute pseudorapidity difference between the two leptons in the dilepton channel.

ttbb at 13 TeV (ATLAS_2018_I1705857)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2017-12 | submitted to JHEP | arXiv:1811.12113

This paper presents measurements of $t\bar{t}$ production in association with additional $b$-jets in $pp$ collisions at the LHC at a centre-of-mass energy of 13 TeV. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 36.1 fb$^{-1}$. Fiducial cross-section measurements are performed in the dilepton and lepton-plus-jets $t\bar{t}$ decay channels. Results are presented at particle level in the form of inclusive cross-sections of $t\bar{t}$ final states with three and four $b$-jets as well as differential cross-sections as a function of global event properties and properties of $b$-jet pairs. The measured inclusive fiducial cross-sections generally exceed the $t\bar{t}b\bar{b}$ predictions from various next-to-leading-order matrix element calculations matched to a parton shower but are compatible within the total uncertainties. The experimental uncertainties are smaller than the uncertainties in the predictions. Comparisons of state-of-the-art theoretical predictions with the differential measurements are shown and good agreement with data is found for most of them.

WWbb at 13 TeV (ATLAS_2018_I1677498)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2017-05 | Phys.Rev.Lett. 121 (2018) no.15, 152002 | arXiv:1806.04667

This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a $W$ boson and a $b$-quark are significant. Events with exactly two leptons ($ee$, $\mu\mu$, or $e\mu$) and two $b$-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb$^{-1}$ of proton-proton collision data taken at $\sqrt{s}=13$ TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within $2\sigma$ of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.

Differential $t\bar{t}$ $l$+jets cross-sections at 13 TeV (ATLAS_2018_I1656578)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2017-01 | Submitted to JHEP | arXiv:1802.06572

Measurements of differential cross sections of top quark pair production in association with jets by the ATLAS experiment at the LHC are presented. The measurements are performed as functions of the top quark transverse momentum, the transverse momentum of the top quark-antitop quark system and the out-of-plane transverse momentum using data from pp collisions at $\sqrt{s}=13$ TeV collected by the ATLAS detector at the LHC in 2015 and corresponding to an integrated luminosity of 3.2 $\text{fb}^{-1}$. The top quark pair events are selected in the lepton (electron or muon) + jets channel. The measured cross sections, which are compared to several predictions, allow a detailed study of top quark production.

All-hadronic boosted ttbar at 13 TeV (ATLAS_2018_I1646686)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2016-09 | doi:10.17182/hepdata.81709.v1 | arXiv:1801.02052

Measurements are made of differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and $t\bar{t}$ system kinematic observables using proton--proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV. The data set corresponds to an integrated luminosity of 36.1 fb${}^{-1}$, recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Events with two large-radius jets in the final state, one with transverse momentum pT>500 GeV and a second with $p_\text{T} > 350$ GeV, are used for the measurement. The top-quark candidates are separated from the multijet background using jet substructure information and association with a $b$-tagged jet. The measured spectra are corrected for detector effects to a particle-level fiducial phase space and a parton-level limited phase space, and are compared to several Monte Carlo simulations by means of calculated $\chi^2$ values. The cross-section for $t\bar{t}$ production in the fiducial phase-space region is 292$\pm$7 (stat)$\pm$76(syst) fb, to be compared to the theoretical prediction of 384$\pm$36 fb.

ATLAS Inclusive jet and dijet cross section measurement at sqrt(s)=13TeV (ATLAS_2018_I1634970)

Inspire | HepData | Analysis reference | JHEP 1805 (2018) 195 | arXiv:1711.02692

Inclusive jet and dijet cross-sections are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV. The measurement uses a dataset with an integrated luminosity of 3.2 fb$^{-1}$ recorded in 2015 with the ATLAS detector at the Large Hadron Collider. Jets are identified using the anti-$k_\text{t}$ algorithm with a radius parameter value of $R = 0.4$. The inclusive jet cross-sections are measured double-differentially as a function of the jet transverse momentum, covering the range from 100 GeV to 3.5 TeV, and the absolute jet rapidity up to $|y| = 3$. The double-differential dijet production cross-sections are presented as a function of the dijet mass, covering the range from 300 GeV to 9 TeV, and the half absolute rapidity separation between the two leading jets within $|y| < 3$, $y^\ast$, up to $y^\ast = 3$. Next-to-leading-order, and next-to-next-to-leading-order for the inclusive jet measurement, perturbative QCD calculations corrected for non-perturbative and electroweak effects are compared to the measured cross-sections.

Soft-Drop Jet Mass at 13 TeV (ATLAS_2017_I1637587)

Inspire | HepData | Analysis reference | ATLAS-STDM-2017-04 | Phys.Rev.Lett. 121 (2018) no.9, 092001 | doi:10.1103/PhysRevLett.121.092001 | arXiv:1711.08341

Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by theoretical calculations, but there has never been a direct comparison between data and calculations of jet substructure observables that are accurate beyond leading-logarithm approximation. Such observables are significant not only for probing the collinear regime of QCD that is largely unexplored at a hadron collider, but also for improving the understanding of jet substructure properties that are used in many studies at the Large Hadron Collider. This Letter documents a measurement of the first jet substructure quantity at a hadron collider to be calculated at next-to-next-to-leading-logarithm accuracy. The normalized, differential cross section is measured as a function of $\text{log}_{10}\rho^2$, where $\rho$ is the ratio of the soft-drop mass to the ungroomed jet transverse momentum. This quantity is measured in dijet events from 32.9fb$^{-1}$ of $\sqrt{s} = 13$ TeV proton-proton collisions recorded by the ATLAS detector. The data are unfolded to correct for detector effects and compared to precise QCD calculations and leading-logarithm particle-level Monte Carlo simulations.

Dileptonic $t\bar{t}$ at 8 TeV (ATLAS_2017_I1626105)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2015-02 | Eur.Phys.J. C77 (2017) no.11, 804 | doi:10.1140/epjc/s10052-017-5349-9 | arXiv:1709.09407

This paper presents single lepton and dilepton kinematic distributions measured in dileptonic $t\bar{t}$ events produced in 20.2 fb${}^{-1}$ of $\sqrt{s} = 8$ TeV $pp$ collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge $e\mu$ pair and one or two $b$-tagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass, a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of $m_t^\text{pole} = 173.2 \pm 0.9 \pm 0.8 \pm 1.2$ GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical sources.

Study of ordered hadron chains at 7 TeV (ATLAS_2017_I1624693)

Inspire | HepData | Analysis reference | ATLAS-STDM-2014-08 | Phys.Rev. D96 (2017) no.9, 092008 | doi:10.1103/PhysRevD.96.092008 | arXiv:1709.07384

The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of 190 $\mu\text{b}^{-1}$ of minimum-bias events collected with proton-proton collisions at a center-of-mass energy $\sqrt{s}$ = 7 TeV in the early low-luminosity data taking with the ATLAS detector at the LHC.

Resolved and boosted ttbar l+jets cross sections at 13 TeV (ATLAS_2017_I1614149)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2016-01 | JHEP 1711 (2017) 191 | doi:10.1007/JHEP11(2017)1 | arXiv:1708.00727

Measurements of differential cross-sections of top-quark pair production in fiducial phase-spaces are presented as a function of top-quark and $t\bar{t}$ system kinematic observables in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. The data set corresponds to an integrated luminosity of 3.2 fb${}^{-1}$, recorded in 2015 with the ATLAS detector at the CERN Large Hadron Collider. Events with exactly one electron or muon and at least two jets in the final state are used for the measurement. Two separate selections are applied that each focus on different top-quark momentum regions, referred to as resolved and boosted topologies of the $t\bar{t}$ final state. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations by means of calculated $\chi^2$ and $p$-values.

Multijet transverse energy-energy correlations (TEEC) at 8 TeV (ATLAS_2017_I1609253)

Inspire | HepData | Analysis reference | ATLAS-STDM-2016-10 | submitted to EPJC | arXiv:1707.02562

Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to $\sqrt{s} = 8$ TeV proton-proton collisions with an integrated luminosity of 20.2 fb$^{-1}$. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of $\alpha_\text{s}(\mu)$ predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy-energy correlation distributions yields $\alpha_\text{s}(m_Z) = 0.1162\pm 0.0011\text{(exp.)}^{+0.0084}_{-0.0070}\text{(theo.)}$, while a global fit to the asymmetry distributions yields a value of $\alpha_\text{s}(m_Z) = 0.1196\pm 0.0013\text{(exp.)}^{+0.0075}_{-0.0045}\text{(theo.)}$.

ATLAS Inclusive jet cross section measurement at sqrt(s)=8TeV (ATLAS_2017_I1604271)

Inspire | HepData | Analysis reference | ATLAS-STDM-2015-01 | JHEP 09 (2017) 020 | arXiv:1706.03192

Inclusive jet production cross-sections are measured in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=8$ TeV recorded by the ATLAS experiment at the Large Hadron Collider at CERN. The total integrated luminosity of the analysed data set amounts to 20.2 fb$^{-1}$. Double-differential cross-sections are measured for jets defined by the anti-$k_\text{t}$ jet clustering algorithm with radius parameters of $R=0.4$ and $R=0.6$ and are presented as a function of the jet transverse momentum, in the range between 70 GeV and 2.5 TeV and in six bins of the absolute jet rapidity, between 0 and 3.0. The measured cross-sections are compared to predictions of quantum chromodynamics, calculated at next-to-leading order in perturbation theory, and corrected for non-perturbative and electroweak effects. The level of agreement with predictions, using a selection of different parton distribution functions for the proton, is quantified. Tensions between the data and the theory predictions are observed.

ttbar + gamma at 8 TeV (ATLAS_2017_I1604029)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2015-21 | JHEP 1711 (2017) 086 | doi:10.1007/JHEP11(2017) | arXiv:1706.03046

The cross section of a top-quark pair produced in association with a photon is measured in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV with 20.2 fb${}^{-1}$ of data collected by the ATLAS detector at the Large Hadron Collider in 2012. The measurement is performed by selecting events that contain a photon with transverse momentum $p_\text{T} > 15$ GeV, an isolated lepton with large transverse momentum, large missing transverse momentum, and at least four jets, where at least one is identified as originating from a $b$-quark. The production cross section is measured in a fiducial region close to the selection requirements. It is found to be $139 \pm 7$ (stat.) $\pm 17$ (syst.) fb, in good agreement with the theoretical prediction at next-to-leading order of $151 \pm 24$ fb. In addition, differential cross sections in the fiducial region are measured as a function of the transverse momentum and pseudorapidity of the photon.

Track-based underlying event at 13 TeV in ATLAS (ATLAS_2017_I1509919)

Inspire | HepData | Analysis reference | ATLAS-STDM-2016-07 | arXiv:1701.05390

We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton-proton collisions at a centre-of-mass energy of 13 TeV, in low-luminosity Large Hadron Collider fills corresponding to an integrated luminosity of 1.6 nb${}^{-1}$. The distributions were constructed using charged particles with absolute pseudorapidity less than 2.5 and with transverse momentum greater than 500 MeV, in events with at least one such charged particle with transverse momentum above 1 GeV. These distributions characterise the angular distribution of energy and particle flows with respect to the charged particle with highest transverse momentum, as a function of both that momentum and of charged-particle multiplicity. The results have been corrected for detector effects and are compared to the predictions of various Monte Carlo event generators, experimentally establishing the level of underlying-event activity at LHC Run 2 energies and providing inputs for the development of event generator modelling. The current models in use for UE modelling typically describe this data to 5% accuracy, compared with data uncertainties of less than 1%.

ttbar + jets at 13 TeV (ATLAS_2017_I1495243)

Inspire | HepData | Analysis reference | Eur.Phys.J. C77 (2017) no.4, 220 | doi:10.1140/epjc/s10052-017-4766-0 | arXiv:1610.09978

Measurements of jet activity in top-quark pair events produced in proton--proton collisions are presented, using 3.2 fb$^{-1}$ of $pp$ collision data at a centre-of-mass energy of 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events are chosen by requiring an opposite-charge $e\mu$ pair and two $b$-tagged jets in the final state. The normalised differential cross-sections of top-quark pair production are presented as functions of additional-jet multiplicity and transverse momentum, $p_\text{T}$. The fraction of signal events that do not contain additional jet activity in a given rapidity region, the gap fraction, is measured as a function of the $p_\text{T}$ threshold for additional jets, and is also presented for different invariant mass regions of the $e\mu b\bar{b}$ system. All measurements are corrected for detector effects and presented as particle-level distributions compared to predictions with different theoretical approaches for QCD radiation. While the kinematics of the jets from top-quark decays are described well, the generators show differing levels of agreement with the measurements of observables that depend on the production of additional jets.

Hard double-parton scattering in four-jet events at 7 TeV (ATLAS_2016_I1479760)

Inspire | HepData | Analysis reference | ATLAS-STDM-2015-08 | arXiv:1608.01857

Inclusive four-jet events produced in $pp$ collisions at a centre-of-mass energy of $\sqrt{s} = 7$ TeV have been analysed for the presence of hard double-parton scattering using data corresponding to an integrated luminosity of $(37.3 \pm 1.3)$ $\mathrm{pb}^{-1}$, collected with the ATLAS detector at the LHC. The distributions of observables sensitive to the contribution of hard double-parton scattering are provided for events containing at least four jets with $p_{\mathrm{T}} \geq 20$ GeV and $\eta \leq 4.4$, and at least one of which has $p_{\text{T}} \geq 42.5$ GeV.

Dileptonic $e \mu$ $t\bar{t}$ early cross-section measurement at 13 TeV (ATLAS_2016_I1468168)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2015-09 | Submitted to PLB | arXiv:1606.02699

This paper describes a measurement of the inclusive top quark pair production cross-section ($\sigma_{t\bar{t}}$) with a data sample of 3.2 fb${}^{-1}$ of proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electron-muon pair in the final state. Jets containing $b$-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two $b$-tagged jets are counted and used to determine simultaneously $\sigma_{t\bar{t}}$ and the efficiency to reconstruct and $b$-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be: $\sigma_{t\bar{t}} = 818 \pm 8$ (stat) $\pm 27$ (syst) $\pm 19$ (lumi) $\pm 12$ (beam) pb, where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4\%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented.

Measurement of the inelastic proton--proton cross-section at $\sqrt{s} = 13\,\text{TeV}$ (ATLAS_2016_I1468167)

Inspire | HepData | Analysis reference | ATLAS-STDM-2015-05 | arXiv:1606.02625

Inelastic cross-section is measured for $\xi > 1 \times 10^{-6}$, where $\xi=M_X^2/s$ is calculated from the invariant mass, $M_X$, of hadrons selected using the largest rapidity gap in the event.

Track-based minimum bias with low-pT tracks at 13 TeV (ATLAS_2016_I1467230)

Inspire | HepData | Analysis reference | ATLAS-STDM-2015-17 | Eur.Phys.J. C76 (2016) no.9, 502 | doi:10.1140/epjc/s10052-016-4335-y | arXiv:1606.01133

Measurements of distributions of charged particles produced in proton-proton collisions with a centre-of-mass energy of 13 TeV are presented. The data were recorded by the ATLAS detector at the LHC and correspond to an integrated luminosity of 151 $\mu$b$^{-1}$. The particles are required to have a transverse momentum greater than 100 MeV and an absolute pseudorapidity less than 2.5. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on multiplicity are measured in events containing at least two charged particles satisfying the above kinematic criteria. The results are corrected for detector effects and compared to the predictions from several Monte Carlo event generators.

Charge asymmetry in top quark pair production in dilepton channel (ATLAS_2016_I1449082)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2015-08 | Phys.Rev. D94 (2016) no.3, 032006 | doi:10.1103/PhysRevD.94.032006 | arXiv:1604.05538

Measurements of the top-antitop quark pair production charge asymmetry in the dilepton channel are presented using data corresponding to an integrated luminosity of $20.3 \text{fb}^{-1}$ from $pp$ collisions at a center-of-mass energy of $\sqrt{s} = 8$ TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the $t\bar{t}$ system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance (at least 2 leptons and 2 jets with $p_\text{T} > 25$ GeV and $|\eta| < 2.5$). Two observables are studied: $A_C^{\ell\ell}$ based on the selected leptons and $A_C^{t\bar{t}}$ based on the reconstructed $t\bar{t}$ final state. The unfolded distributions of $\Delta|\eta| = |\eta|_{\ell^+} - |\eta|_{\ell^-}$ and $\Delta|y| = |y|_\text{top} - |y|_\text{antitop}$ are provided. USERS SHOULD NOTE THAT EXPLICIT RECONSTRUCTION OF INDIVIDUAL STANDARD MODEL NEUTRINOS IS USED IN THIS ANALYSIS ROUTINE TO MATCH THE MONTE-CARLO-BASED CORRECTION TO THE FIDUCIAL REGION APPLIED IN THE PAPER.

Track-based minimum bias at 8 TeV (ATLAS_2016_I1426695)

Inspire | HepData | Analysis reference | ATLAS-STDM-2014-19 | Eur.Phys.J. C76 (2016) no.7, 403 | doi:10.1140/epjc/s10052-016-4203-9 | arXiv:1603.02439

This paper presents measurements of distributions of charged particles which are produced in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV and recorded by the ATLAS detector at the LHC. A special dataset recorded in 2012 with a small number of interactions per beam crossing (below 0.004) and corresponding to an integrated luminosity of 160 $\mu\text{b}^{-1}$ was used. A minimum-bias trigger was utilised to select a data sample of more than 9 million collision events. The multiplicity, pseudorapidity, and transverse momentum distributions of charged particles are shown in different regions of kinematics and charged-particle multiplicity, including measurements of final states at high multiplicity. The results are corrected for detector effects and are compared to the predictions of various Monte Carlo event generator models which simulate the full hadronic final state.

Track-based minimum bias at 13 TeV in ATLAS (ATLAS_2016_I1419652)

Inspire | HepData | Analysis reference | ATLAS-STDM-2015-02 | arXiv:1602.01633 | doi:10.1016/j.physletb.2016.04.050 | Physics Letters B (2016), Vol. 758, pp. 67-88

Measurements from proton-proton collisions at centre-of-mass energy of $\sqrt{s} = 13$ TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. The observed distributions are corrected to well-defined phase-space regions ($p_\text{T} > 500$ MeV and $|\eta| < 2.5$ of the particles), using model-independent corrections.

Number of tracks in jets (ATLAS_2016_I1419070)

Inspire | HepData | Analysis reference | ATLAS-STDM-2015-12 | arXiv:1602.00988 | Eur.Phys.J. C76 (2016) no.6, 322 | doi:10.1140/epjc/s10052-016-4126-5

The number of charged particles inside jets is a widely used discriminant for identifying the quark or gluon nature of the initiating parton and is sensitive to both the perturbative and non-perturbative components of fragmentation. This analysis presents a measurement of the average number of charged particles with $p_\text{T}>500$ MeV inside high-momentum jets in dijet events using 20.3 fb${}^{-1}$ of data recorded with the ATLAS detector in $pp$ collisions at $\sqrt{s}=8$ TeV collisions at the LHC. The jets considered have transverse momenta from 50 GeV up to and beyond 1.5 TeV. The reconstructed charged-particle track multiplicity distribution is unfolded to remove distortions from detector effects.

Inclusive jet cross sections using early 13 TeV data (ATLAS_2016_CONF_2016_092)

Analysis reference | ATLAS-CONF-2016-092

This note presents the measurement of inclusive-jet cross-sections in proton--proton collisions at a centre-of-mass energy of 13TeV. The measurement uses data corresponding to an integrated luminosity of 3.2 fb$^{-1}$ collected with the ATLAS detector at the Large Hadron Collider in 2015. Jets are clustered using the anti-$k_\text{t}$ algorithm with a radius parameter value of $R = 0.4$. Double differential inclusive-jet cross-sections are presented as a function of the jet transverse momentum, covering the range from 100 GeV to about 3.2 TeV, and of the absolute jet rapidity, up to $|y| = 3$. The predictions of next-to-leading-order QCD calculations using several parton distribution function (PDF) sets and corrected for non-perturbative and electroweak effects are compared to the measured cross-sections. The predictions are consistent with the measured cross-sections within uncertainties.

ttbar (to l+jets) differential cross sections at 8 TeV (ATLAS_2015_I1404878)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2015-06 | Submitted to EPJC | arXiv:1511.04716

Measurements of normalized differential cross-sections of top-quark pair production are presented as a function of the top-quark, $t\bar{t}$ system and event-level kinematic observables in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV. The observables have been chosen to emphasize the $t\bar{t}$ production process and to be sensitive to effects of initial- and final-state radiation, to the different parton distribution functions, and to non-resonant processes and higher-order corrections. The dataset corresponds to an integrated luminosity of 20.3 fb${}^{-1}$, recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton$+$jets channel, requiring exactly one charged lepton and at least four jets with at least two of the jets tagged as originating from a $b$-quark. The measured spectra are corrected for detector effects and are compared to several Monte Carlo simulations. The results are in fair agreement with the predictions over a wide kinematic range. Nevertheless, most generators predict a harder top-quark transverse momentum distribution at high values than what is observed in the data. Predictions beyond NLO accuracy improve the agreement with data at high top-quark transverse momenta. Using the current settings and parton distribution functions, the rapidity distributions are not well modelled by any generator under consideration. However, the level of agreement is improved when more recent sets of parton distribution functions are used.

Boosted ttbar differential cross-section (ATLAS_2015_I1397637)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2014-15 | Phys.Rev. D93 (2016) no.3, 032009 | doi:10.1103/PhysRevD.93.032009 | arXiv:1510.03818

The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3fb${}^{-1}$ of proton-proton collisions at a center-of-mass energy of 8 TeV. The measurement is performed for $t\bar{t}$ events in the lepton+jets channel. The cross-section is reported as a function of the hadronically decaying top quark transverse momentum for values above 300 GeV. The hadronically decaying top quark is reconstructed as an anti-$k_\text{t}$ jet with radius parameter $R=1.0$ and identified with jet substructure techniques. The observed yield is corrected for detector effects to obtain a cross-section at particle level in a fiducial region close to the event selection.

$Wt$ at 8 TeV (ATLAS_2015_I1397635)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2012-20 | JHEP01 (2016) 064 | doi:10.1007/JHEP01(2016)064 | arXiv:1510.03752

Fiducial cross-section for $Wt+t\bar{t}$ production in events with two leptons and exactly one jet, 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 for the production of a top quark and a $W$ boson is measured in a fiducial acceptance requiring two leptons with $p_\perp > 25$ GeV and $|\eta| < 2.5$, one jet with $p_\perp > 20$ GeV and $|\eta| < 2.5$, and $E^\text{miss}_\text{T} > 20$ GeV, including both $Wt$ and top-quark pair events as signal. The measured value of the fiducial cross-section is $0.85 \pm 0.01$ (stat.) $\pm 0.07$ (syst.) $\pm 0.03$ (lumi.) pb.

Multijets at 8 TeV (ATLAS_2015_I1394679)

Inspire | HepData | Analysis reference | ATLAS-STDM-2014-14 | arXiv:1509.07335

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. The dataset corresponds to an integrated luminosity of 20.3\,fb^{-1}. The cross sections are corrected for detector effects and presented as a function of the jet momenta, invariant masses, minimum and maximum opening angles and other kinematic variables.

Jet charge (ATLAS_2015_I1393758)

Inspire | HepData | Analysis reference | ATLAS-STDM-2014-17 | Phys.Rev. D93 (2016) no.5, 052003 | doi:10.1103/PhysRevD.93.052003 | arXiv:1509.05190

The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum-weighted sums, called jet charge, in dijet events using 20.3 fb${}^{-1}$ of data recorded with the ATLAS detector at $\sqrt{s} = 8$ TeV in $pp$ collisions at the LHC. The jet charge distribution is unfolded to remove distortions from detector effects and the resulting particle-level distribution is compared with several models. The $p_\text{T}$ dependence of the jet charge distribution average and standard deviation are compared to predictions obtained with several leading-order and next-to-leading-order parton distribution functions. The data are also compared to different Monte Carlo simulations of QCD dijet production using various settings of the free parameters within these models. The chosen value of the strong coupling constant used to calculate gluon radiation is found to have a significant impact on the predicted jet charge. There is evidence for a $p_\text{T}$ dependence of the jet charge distribution for a given jet flavor. In agreement with perturbative QCD predictions, the data show that the average jet charge of quark-initiated jets decreases in magnitude as the energy of the jet increases.

$tt+b(b)$ at 8 TeV (ATLAS_2015_I1390114)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2014-10 | Eur.Phys.J. C76 (2016) no.1, 11 | doi:10.1140/epjc/s10052-015-3852-4 | arXiv:1508.06868

Fiducial cross-sections for $t\bar{t}$ production with one or two additional $b$-jets are presented, 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 ($e\mu$, $\mu\mu$, $ee$) 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. NB: When merging several output YODA files, the ratio (d02-x01-y01) needs to be reconstructed in a post-processing step.

Energy-energy correlation (ATLAS_2015_I1387176)

Inspire | HepData | Analysis reference | ATLAS-STDM-2014-03 | arXiv:1508.01579

High transverse momentum jets produced in $pp$ collisions at a centre-of-mass energy of 7 TeV are used to measure the transverse energy--energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of $158\,\text{pb}^{-1}$. The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data are unfolded to the particle level. NB--If the routine is to be run on several samples (with different cross sections), the asymmetry has to be calculated again in a post-processing step using the merged output file.

Colour flow in hadronic top decay at 8 TeV (ATLAS_2015_I1376945)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2014-09 | arXiv:1506.05629

The distribution and orientation of energy inside jets is predicted to be an experimental handle on colour connections between the hard-scatter quarks and gluons initiating the jets. This is a measurement of the distribution of one such variable, the jet pull angle. The pull angle is measured for jets produced in $t\bar{t}$ events with one $W$ boson decaying leptonically and the other decaying to jets using 20.3\,$\text{fb}^{-1}$ of data recorded with the ATLAS detector at a centre-of-mass energy of $\sqrt{s} = 8$\,TeV at the LHC. The jet pull angle distribution is corrected for detector resolution and acceptance effects.

Pseudo-top-antitop cross sections (ATLAS_2015_I1345452)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2013-07 | arXiv:1502.05923

Various differential cross-sections are measured in top-quark pair ($t\bar{t}$) events produced in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the LHC with the ATLAS detector. These differential cross-sections are presented in a data set corresponding to an integrated luminosity of 4.6 fb$^{-1}$. The differential cross-sections are presented in terms of kinematic variables of a top-quark proxy referred to as the pseudo-top-quark whose dependence on theoretical models is minimal. The pseudo-top-quark can be defined in terms of either reconstructed detector objects or stable particles in an analogous way. The measurements are performed on $t\bar{t}$ events in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of them tagged as originating from a $b$-quark. The hadronic and leptonic pseudo-top-quarks are defined via the leptonic or hadronic decay mode of the W boson produced by the top-quark decay in events with a single charged lepton. The cross-section is measured as a function of the transverse momentum and rapidity of both the hadronic and leptonic pseudo-top-quark as well as the transverse momentum, rapidity and invariant mass of the pseudo-top-quark pair system. The measurements are corrected for detector effects and are presented within a kinematic range that closely matches the detector acceptance.

Measurement of the inclusive jet cross-section at 7 TeV (ATLAS_2014_I1325553)

Inspire | HepData | Analysis reference | ATLAS-STDM-2013-11 | arXiv:1410.8857

Measurement of the inclusive jet cross-section in proton--proton collisions at a centre-of-mass energy of 7 TeV using a data set corresponding to an integrated luminosity of 4.5/fb collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-$k_t$ algorithm with radius parameter values of 0.4 and 0.6. The double-differential cross-sections are presented as a function of the jet transverse momentum and the jet rapidity, covering jet transverse momenta from 100 GeV to 2 TeV.

Measurement of jet multiplicity and transverse momentum spectra in top events using full 7 TeV ATLAS dataset (ATLAS_2014_I1304688)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2012-03 | CERN-PH-EP-2014-114 | arXiv:1407.0891[hep-ex]

Measurement of the differential t$\bar{\mathrm t}$ production cross-section in 7 TeV proton-proton collisions in the single-lepton channel from ATLAS. The data comprise the full 2011 data sample corresponding to an integrated luminosity of $4.6\,\mathrm{fb}^{-1}$. The differential cross-sections are measured as a function of the jet multiplicity for up to eight jets using jet transverse momentum thresholds of 25, 40, 60, and 80 GeV, and as a function of jet transverse momentum up to the fifth leading jet. The results after background subtraction are corrected for all detector effects, within a kinematic range closely matched to the experimental acceptance.

Leading jet underlying event at 7 TeV in ATLAS (ATLAS_2014_I1298811)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-31 | arXiv:1406.0392 | Eur.Phys.J. C74 (2014) 2965 | DOI:10.1140/epjc/s10052-014-2965-5

Underlying event measurements with the ATLAS detector at the LHC at a center-of-mass energy of 7 TeV, using the leading jet for event azimuthal orientation and constructing standard transverse region observables from both charged tracks and calorimeter clusters.

The differential production cross section of the $\phi(1020)$ meson in $\sqrt{s}=7$ TeV $pp$ collisions measured with the ATLAS detector (ATLAS_2014_I1282441)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-47 | arXiv:1402.6162 | Eur.Phys.J. C74 (2014) no.7, 2895

A measurement is presented of the $\phi \rightarrow K^+K^-$ production cross section at $\sqrt{s}$ = 7 TeV using pp collision data corresponding to an integrated luminosity of 383 $\mu$b$^{-1}$ collected with the ATLAS experiment at the LHC. Selection of $\phi(1020)$ mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum, $pT,\phi$, and rapidity, $y_\phi$, of the $\phi(1020)$ meson in the fiducial region 500 < $pT,\phi$ < 1200 MeV, |$y_\phi$| < 0.8, kaon $pT,K$ > 230 MeV and kaon momentum $p_K$ < 800 MeV. The integrated $\phi(1020)$ production cross section in this fiducial range is measured to be $\sigma_{\phi \rightarrow K^+K^-}$ = 570 \pm 8 (stat) \pm 66 (syst) \pm 20 (lumi) $\mu$b.

High-mass dijet cross section (ATLAS_2014_I1268975)

Inspire | HepData | Analysis reference | arXiv:1312.3524 | JHEP 1405 (2014) 059

Double-differential dijet cross sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of dijet mass and rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5/fb, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross sections are presented at the particle level. Cross sections are measured up to 5 TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6. The cross sections are compared with next-to-leading-order perturbative QCD calculations by NLOJET++ corrected to account for non-perturbative effects. Comparisons with POWHEG predictions, using a next-to-leading-order matrix element calculation interfaced to a parton-shower Monte Carlo simulation, are also shown. Electroweak effects are accounted for in both cases. The quantitative comparison of data and theoretical predictions obtained using various parameterizations of the parton distribution functions is performed using a frequentist method. An example setting a lower limit on the compositeness scale for a model of contact interactions is presented, showing that the unfolded results can be used to constrain contributions to dijet production beyond that predicted by the Standard Model.

Measurement of jet shapes in top quark pair events at $\sqrt{s} = 7$ TeV with ATLAS (ATLAS_2013_I1243871)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-48 | arXiv:1307.5749

Measurement of jet shapes in top pair events in the ATLAS 7 TeV run. b-jets are shown to have a wider energy density distribution than light-quark induced jets.

Flavour composition of dijet events at 7 TeV (ATLAS_2012_I1188891)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-40 | arXiv:1210.0441

The measurement of the flavour composition of dijet events produced in pp collisions at $\sqrt{s}=7 \text{TeV}$ using the ATLAS detector. Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. The fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity $|y| < 2.1$ are measured.

Pseudorapidity dependence of the total transverse energy at 7 TeV (ATLAS_2012_I1183818)

Inspire | HepData | Analysis reference | arXiv:1208.6256

The measurement of the sum of the transverse energy of particles as a function of particle pseudorapidity, eta, in proton-proton collisions at a centre-of-mass energy, $\sqrt{s} = 7 \text{TeV}$ using the ATLAS detector at the Large Hadron Collider. The measurements are performed in the region $|\eta| < 4.8$ for two event classes: those requiring the presence of particles with a low transverse momentum and those requiring particles with a significant transverse momentum (dijet events where both jets have $E_T > 20$ GeV). In the second dataset measurements are made in the region transverse to the hard scatter.

Studies of the underlying event at 7 TeV with track-jets (ATLAS_2012_I1125575)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-30 | arXiv:1208.0563

Distributions sensitive to the underlying event are studied in events containing one or more charged particles. Jets are reconstructed using the anti-$k_t$ algorithm with radius parameter $R$ varying between 0.2 and 1.0. Distributions of the charged-particle multiplicity, the scalar sum of the transverse momentum of charged particles, and the average charged-particle pT are measured as functions of $p_\perp^\text{jet}$ in regions transverse to and opposite the leading jet for $4 \text{GeV} < p_\perp^\text{jet} < 100 \text{GeV}$. In addition, the $R$-dependence of the mean values of these observables is studied.

Measurement of charged-particle event shape variables (ATLAS_2012_I1124167)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-32 | arXiv:1207.6915 | Phys.Rev. D88 (2013) 032004 | 10.1103/PhysRevD.88.032004

The measurement of charged-particle event shape variables is presented in inclusive inelastic $pp$ collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state charged particles momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged-particle transverse momentum, charged-particle multiplicity, and summed transverse momentum is presented.

Jet shapes and jet masses (ATLAS_2012_I1119557)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-38 | Phys.Rev. D86 (2012) 072006 | doi:10.1103/PhysRevD.86.072006 | arXiv:1206.5369

Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of $\sqrt{s} = 7$ TeV. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-$k_t$ algorithm with distance parameters $R = 0.6$ and 1.0, with transverse momentum $pT > 300$ GeV and pseudorapidity $|\eta| < 2$.

$b$-hadron production cross-section using decays to $D^*\mu^-X$ at $\sqrt{s} = 7$ TeV (ATLAS_2012_I1118269)

Inspire | HepData | Analysis reference | ATLAS-BPHY-2011-02 | arXiv:1206.3122

Measurement of $b$-hadron production cross section using 3.3 pb$^{-1}$ of integrated luminosity, collected during the 2010 LHC run. The $b$-hadrons are selected by partially reconstructing $D^{*}\mu^-X$ final states using only direct semileptonic decays of $b$ to $D^*\mu^-X$. Differential cross sections as functions of $p_\perp$ and $|\eta|$.

Measurement of ttbar production with a veto on additional central jet activity (ATLAS_2012_I1094568)

Inspire | HepData | Analysis reference | ATLAS-TOPQ-2011-21 | arXiv:1203.5015 | Eur.Phys.J. C72 (2012) 2043

A measurement of the additional jet activity in dileptonic ttbar events. The fraction of events passing a veto requirement are shown as a function the veto scale for four central rapidity intervals. Two veto definitions are used: events are vetoed if they contain an additional jet in the rapidity interval with transverse momentum above a threshold, or alternatively, if the scalar transverse momentum sum of all additional jets in the rapidity interval is above a threshold.

Jet mass and substructure of inclusive jets at 7 TeV (ATLAS_2012_I1094564)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-19 | JHEP 1205 (2012) 128 | doi:10.1007/JHEP05(2012)128 | arXiv:1203.4606

In this analysis, the assumption that the internal substructure of jets generated by QCD radiation is well understood is tested on an inclusive sample of jets recorded with the ATLAS detector in 2010, which corresponds to 35 $pb^{-1}$ of $pp$ collisions delivered by the LHC at $\sqrt{s} = 7$ TeV. Jet invariant mass, $k_{t}$ splitting scales and $N$-subjettiness variables are presented for anti-$k_{t}$ $R = 1.0$ jets and Cambridge-Aachen $R = 1.2$ jets. Jet invariant-mass spectra for Cambridge-Aachen $R = 1.2$ jets after a splitting and filtering procedure are also presented.

ATLAS_2012_I1093734

Inspire | HepData

Azimuthal ordering of charged hadrons (ATLAS_2012_I1091481)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-20 | CERN-PH-EP-2011-197 | arXiv:1203.0419

Measurement of the ordering of charged hadrons in the azimuthal angle relative to the beam axis at the Large Hadron Collider (LHC). A spectral analysis of correlations between longitudinal and transverse components of the momentum of the charged hadrons is performed. Data were recorded with the ATLAS detector at centre-of-mass energies of $\sqrt{s} = 900 \text{GeV}$ and $\sqrt{s} = 7 \text{TeV}$. The correlations measured in a phase space region dominated by low-$p_\perp$ particles are not well described by conventional models of hadron production. The measured spectra show features consistent with the fragmentation of a QCD string represented by a helix-like ordered gluon chain. Beam energy must be specified (in GeV) as analysis option "ENERGY" when rivet-merging samples.

Rapidity gap cross sections measured with the ATLAS detector in $pp$ collisions at $\sqrt{s} = 7$ TeV. (ATLAS_2012_I1084540)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-01 | arXiv:1201.2808

Pseudorapidity gap distributions in proton-proton collisions at $\sqrt{s} = 7$ TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 inverse microbarns. Cross sections are measured differentially in terms of $\Delta \eta_F$, the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at $\eta = \pm 4.9$, in which no final state particles are produced above a transverse momentum threshold $p_\perp$ cut. The measurements span the region $0 < \Delta \eta_F < 8$ for $200 < p_T\text{ cut} < 800 \text{MeV}$. At small $\Delta \eta_F$, the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process ($pp \to Xp$), enhanced by double dissociation ($pp \to XY$) where the invariant mass of the lighter of the two dissociation systems satisfies $M_Y \lesssim 7 \text{GeV}$. The resulting cross section is $\mathrm{d} \sigma / \mathrm{d} \Delta \eta_F \sim 1$ mb for $\Delta \eta_F \gtrsim 3$. The large rapidity gap data are used to constrain the value of the pomeron intercept appropriate to triple Regge models of soft diffraction. The cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements.

Inclusive jet and dijet cross sections at 7 TeV (ATLAS_2012_I1082936)

Inspire | HepData | Analysis reference | arXiv:1112.6297v2 | CERN-PH-EP-2011-192

Inclusive jet and dijet cross sections have been measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector at the Large Hadron Collider. The cross sections were measured using jets clustered with the anti-kT algorithm with parameters R=0.4 and R=0.6. These measurements are based on the 2010 data sample, consisting of a total integrated luminosity of 37 inverse picobarns. Inclusive jet double-differential cross sections are presented as a function of jet transverse momentum, in bins of jet rapidity. Dijet double-differential cross sections are studied as a function of the dijet invariant mass, in bins of half the rapidity separation of the two leading jets. The measurements are performed in the jet rapidity range $|y|<4.4$, covering jet transverse momenta from 20 GeV to 1.5 TeV and dijet invariant masses from 70 GeV to 5 TeV. This is the successor analysis of ATLAS_2010_S8817804

$D^{*\pm}$ production in jets (ATLAS_2012_I1082009)

Inspire | HepData | Analysis reference | arXiv:1112.4432

Measurement of $D^{*\pm}$ meson production in jets from proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the LHC. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of $0.30\,\text{pb}^{-1}$ for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range $|eta| < 2.5$.

$K_S^0$ and $\Lambda$ production at 0.9 and 7 TeV with ATLAS (ATLAS_2011_I944826)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-09 | arXiv:1111.1297v2 | Phys.Rev. D85 (2012) 012001

The production of $K_S$ and $\Lambda$ hadrons is studied in inelastic $pp$ collisions at $\sqrt{s} = 0.9$ and 7 TeV collected with the ATLAS detector at the LHC using a minimum-bias trigger. The observed distributions of transverse momentum, rapidity, and multiplicity are corrected to hadron level in a model-independent way within well defined phase-space regions. The distribution of the production ratio of $\bar{\Lambda}$ to $\Lambda$ baryons is also measured. The results are compared with various Monte Carlo simulation models. Although most of these models agree with data to within 15 percent in the $K_S$ distributions, substantial disagreements with data are found in the $\Lambda$ distributions of transverse momentum. Beam energy must be specified (in GeV) as analysis option "ENERGY" when rivet-merging samples.

Inclusive and dijet cross-sections of $b$-jets in $pp$ collisions at $\sqrt{s} = 7$ TeV with ATLAS (ATLAS_2011_I930220)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-15 | Eur.Phys.J. C71 (2011) 1846 | arXiv:1109.6833

The inclusive and dijet production cross-sections have been measured for jets containing $b$-hadrons ($b$-jets) in proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 7$ TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb$^-1$. The $b$-jets are identified using either a lifetime-based method, where secondary decay vertices of $b$-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of $b$-hadrons inside jets. The inclusive $b$-jet cross-section is measured as a function of transverse momentum in the range $20 < pT < 400$ GeV and rapidity in the range $|y| < 2.1$. The $b\bar{b}$-dijet cross-section is measured as a function of the dijet invariant mass in the range $110 < $m_{jj}$ < 760$ GeV, the azimuthal angle difference between the two jets and the angular variable $\chi$ in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG+Pythia6. MC@NLO+Herwig shows good agreement with the measured $b\bar{b}$-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central $b$-jets with large transverse momenta.

Jet fragmentation at 7 TeV (ATLAS_2011_I929691)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-14 | Eur.Phys.J.C 71 (2011) 1795 | doi:10.1140/epjc/s10052-011-1795-y | arXiv:1109.5816

The jet fragmentation function and transverse profile for jets with 25 GeV $< p_\text{T jet} < 500$ GeV and $|\eta_\text{jet}| < 1.2$ produced in proton-proton collisions with a center-of-mass energy of 7 TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb${}^{-1}$. Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. None of these choices reproduce both the transverse profile and fragmentation function over the full kinematic range of the measurement.

Measurement of electron and muon differential cross-section from heavy-flavour decays (ATLAS_2011_I926145)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-07 | CERN-PH-EP-2011-108 | arXiv:1109.0525

Measurement of inclusive electron and muon cross sections for $7 < p_\perp <26$ GeV in $|\eta| <2.0$, excluding $1.37<|\eta|<1.52$, and muon cross section for $4 < p_\perp < 100$ GeV in $|\eta| <2.50$. The $W/Z/\gamma^*$ component must be subtracted to leave the heavy flavour contribution.

Measurement of ATLAS track jet properties at 7 TeV (ATLAS_2011_I919017)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-14 | Phys.Rev.D 84 (2011) 054001 | doi:10.1103/PhysRevD.84.054001 | arXiv:1107.3311 | ATLAS-STDM-2010-14 | CERN-PH-EP-2011-110

ATLAS measurement of track jet pT, multiplicity per jet, longitudinal fragmentation, transverse momentum, radius w.r.t jet axis distributions, with jets constructed from charged tracks with $pT > 300$ MeV, using the anti-$k_T$ jet algorithm with $R = 0.4, 0.6$.

Measurement of the inelastic proton-proton cross-section at $\sqrt{s} = $7 TeV. (ATLAS_2011_I894867)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-11 | arXiv:1104.0326

Inelastic cross-section is measured for $\xi > 5 \times 10^{-6}$, where $\xi=M_X^2/s$ is calculated from the invariant mass, $M_X$, of hadrons selected using the largest rapidity gap in the event.

Measurement of multi-jet cross sections (ATLAS_2011_S9128077)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-12 | arXiv:1107.2092

Inclusive multi-jet production is studied using an integrated luminosity of 2.4 pb-1. Results on multi-jet cross sections are presented differential in pT of the four leading jets, HT. Additionally three-to-two jet fractions are presented differential in different observables. Jets are anti-$k_t$ with $R=0.4$ and $R=0.6$, $p_\perp>80(60)$ GeV and $|\eta|<2.8$.

Measurement of dijet production with a veto on additional central jet activity (ATLAS_2011_S9126244)

Inspire | HepData | Analysis reference | ATLAS-STDM-2011-03 | arXiv:1107.1641

A measurement of the jet activity in rapidity intervals bounded by a dijet system. The fraction of events passing a veto requirement are shown as a function of both the rapidity interval size and the average transverse momentum of the dijet system. The average number of jets above the veto threshold are also shown as a function of the same variables. There are two possible selection criteria applied to data. Either the two highest transverse momentum jets or the jets most forward and backward in rapidity are taken to define the dijet system, where the veto threhsold is 20 GeV. Additionally for the latter selection an alternative veto transverse momentum threshold which is equal to the average transverse momentum is applied. Jet selections are based on the anti-$k_t$ algorithm with $R=0.6$, $p_\perp > 20$ GeV and $|y_\text{jet}| < 4.4$.

Measurement of J/Psi production (ATLAS_2011_S9035664)

Inspire | HepData | Analysis reference | ATLAS-BPHY-2010-01 | arXiv:1104.3038

The inclusive $J/\psi$ production cross-section and fraction of $J/\psi$ mesons produced in B-hadron decays are measured in proton-proton collisions at $\sqrt{s} = 7$ TeV with the ATLAS detector at the LHC, as a function of the transverse momentum and rapidity of the J/psi, using 2.3$\textrm{pb}^{-1}$ of integrated luminosity. The cross section is measured from a minimum $p_T$ of 1 GeV to a maximum of 70 GeV and for rapidities within $|y| < 2.4$ giving the widest reach of any measurement of $J/\psi$ production to date.

Calo-based underlying event at 900 GeV and 7 TeV in ATLAS (ATLAS_2011_S8994773)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-05 | arXiv:1103.1816

Underlying event measurements with the ATLAS detector at the LHC at center-of-mass energies of 900 GeV and 7 TeV, using calorimeter clusters rather than charged tracks. Beam energy must be specified (in GeV) as analysis option "ENERGY" when rivet-merging samples.

Dijet azimuthal decorrelations (ATLAS_2011_S8971293)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-13 | arXiv:1102.2696

Dijet azimuthal decorrelation measured by ATLAS at 7 TeV. Jets are anti-$k_t$ with $R = 0.6$, $p_\perp > 100$ GeV, $|\eta| < 0.8$. The analysis is binned in leading jet $p_\perp$ bins. All data is fully corrected for detector effects.

Jet shapes at 7 TeV in ATLAS (ATLAS_2011_S8924791)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-10 | arXiv:1101.0070

Measurement of jet shapes in inclusive jet production in $pp$ collisions at 7 TeV based on 3 pb$^{-1}$ of data. Jets are reconstructed in $|\eta| < 5$ using the anti-$k_\perp$ algorithm with $30 < p_\perp < 600$ GeV and $|y| < 2.8$.

Cross-section and fragmentation function in anti-$k_t$ track jets (ATLAS_2010_CONF_2010_049)

Inspire | HepData | Analysis reference | ATLAS-CONF-2010-049

Jets are identified and their properties studied using tracks measured by the ATLAS Inner Detector. Events are selected using a minimum-bias trigger, allowing the emergence of jets at low transverse momentum to be observed and for jets to be studied independently of the calorimeter. Jets are reconstructed using the anti-kt algorithm applied to tracks with two parameter choices, 0.4 and 0.6. An inclusive jet transverse momentum cross section measurement from 4 GeV to 80 GeV is shown, integrated over $|\eta| < 0.57$ and corrected to charged particle-level truth jets. The probability that a particular particle carries a fixed fraction of the jet momentum (fragmentation function) is also measured. All data is corrected to the particle level. ATTENTION - Data read from plots!

Track-based minimum bias at 900 GeV and 2.36 and 7 TeV in ATLAS (ATLAS_2010_S8918562)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-06 | arXiv:1012.5104

Measurements from proton-proton collisions at centre-of-mass energies of $\sqrt{s} = 0.9$, 2.36, and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase-space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. Beam energy must be specified (in GeV) as analysis option "ENERGY" when rivet-merging samples.

Track-based underlying event at 900 GeV and 7 TeV in ATLAS (ATLAS_2010_S8894728)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-04 | arXiv:1012.0791

The underlying event measurements with the ATLAS detector at the LHC at the center of mass energies of 900 GeV and 7 TeV. The observables sensitive to the underlying event, i.e the charged particle density and charged pT sum, as well as their standard deviations and the average pT, are measured as functions of the leading track. A track pT cut of 500 MeV is applied for most observables, but the main profile plots are also shown for a lower track cut of 100 MeV, which includes much more of the soft cross-section. The angular distribution of the charged tracks with respect to the leading track is also studied, as are the correlation between mean transverse momentum and charged particle multiplicity, and the `plateau' height as a function of the leading track $|\eta|$. Beam energy must be specified (in GeV) as analysis option "ENERGY" when rivet-merging samples.'

Inclusive jet cross section and di-jet mass and chi spectra at 7 TeV in ATLAS (ATLAS_2010_S8817804)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-03 | arXiv:1009.5908

The first jet cross section measurement made with the ATLAS detector at the LHC. Anti-kt jets with $R=0.4$ and $R=0.6$ are resconstructed within $|y|<2.8$ and above 60 GeV for the inclusive jet cross section plots. For the di-jet plots the second jet must have pT>30 GeV. Jet pT and di-jet mass spectra are plotted in bins of rapidity between $|y| = $ 0.3, 0.8, 1.2, 2.1, and 2.8. Di-jet $\chi$ spectra are plotted in bins of di-jet mass between 340 GeV, 520 GeV, 800 GeV and 1200 GeV.

Charged particles at 900 GeV in ATLAS (ATLAS_2010_S8591806)

Inspire | HepData | Analysis reference | ATLAS-STDM-2010-01 | arXiv:1003.3124

The first measurements with the ATLAS detector at the LHC. Data were collected using a minimum-bias trigger in December 2009 during proton-proton collisions at a centre of mass energy of 900 GeV. The charged- particle density, its dependence on transverse momentum and pseudorapid- ity, and the relationship between transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range $|\eta| < 2.5$ and $p_\perp > 500$ MeV. All data is corrected to the particle level.