Inclusive Top Quark Pair Production Research Articles

Combination of inclusive top-quark pair production cross-section measurements using ATLAS and CMS data at sqrt{s} = 7 and 8 TeV

A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron–muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb−1 at sqrt{s} = 7 TeV and about 20 fb−1 at sqrt{s} = 8 TeV for each experiment. The combined cross-sections are determined to be 178.5 ± 4.7 pb at sqrt{s} = 7 TeV and {243.3}_{-5.9}^{+6.0} pb at sqrt{s} = 8 TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined cross-sections is determined to be R8/7 = 1.363 ± 0.032. The combined measured cross-sections and their ratio agree well with theory calculations using several parton distribution function (PDF) sets. The values of the top-quark pole mass (with the strong coupling fixed at 0.118) and the strong coupling (with the top-quark pole mass fixed at 172.5 GeV) are extracted from the combined results by fitting a next-to-next-to-leading-order plus next-to-next-to-leading-log QCD prediction to the measurements. Using a version of the NNPDF3.1 PDF set containing no top-quark measurements, the results obtained are {m}_t^{textrm{pole}}={173.4}_{-2.0}^{+1.8} GeV and {alpha}_{textrm{s}}left({m}_Zright)={0.1170}_{-0.0018}^{+0.0021} .

Inclusive and differential cross-sections for dilepton toverline{t} production measured in sqrt{s} = 13 TeV pp collisions with the ATLAS detector

Differential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs ( toverline{t} ) are measured using the full LHC Run 2 data sample collected with the ATLAS detector. The data were collected at a pp collision energy of sqrt{s} = 13 TeV and correspond to an integrated luminosity of 140 fb−1. The measurements use events containing an oppositely charged eμ pair and b-tagged jets. The results are compared with predictions from several Monte Carlo generators. While no prediction is found to be consistent with all distributions, a better agreement with measurements of the lepton pT distributions is obtained by reweighting the toverline{t} sample so as to reproduce the top-quark pT distribution from an NNLO calculation. The inclusive top-quark pair production cross-section is measured as well, both in a fiducial region and in the full phase-space. The total inclusive cross-section is found to beσtt¯=829±1stat±13syst±8lumi±2beampb,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\sigma}_{t\\overline{t}}=829\\pm 1\\ \\left(\ extrm{stat}\\right)\\pm 13\\ \\left(\ extrm{syst}\\right)\\pm 8\\ \\left(\ extrm{lumi}\\right)\\pm 2\\ \\left(\ extrm{beam}\\right)\\ \ extrm{pb}, $$\\end{document}where the uncertainties are due to statistics, systematic effects, the integrated luminosity and the beam energy. This is in excellent agreement with the theoretical expectation.

Measurement of the toverline{t} production cross-section in pp collisions at sqrt{s} = 5.02 TeV with the ATLAS detector

The inclusive top-quark pair ( toverline{t} ) production cross-section {sigma}_{toverline{t}} is measured in proton–proton collisions at a centre-of-mass energy sqrt{s} = 5.02 TeV, using 257 pb−1 of data collected in 2017 by the ATLAS experiment at the LHC. The toverline{t} cross-section is measured in both the dilepton and single-lepton final states of the toverline{t} system and then combined. The combination of the two measurements yieldsσtt¯=67.5±0.9stat.±2.3syst.±1.1lumi.±0.2beampb,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\sigma}_{t\\overline{t}}=67.5\\pm 0.9\\left(\ extrm{stat}.\\right)\\pm 2.3\\left(\ extrm{syst}.\\right)\\pm 1.1\\left(\ extrm{lumi}.\\right)\\pm 0.2\\left(\ extrm{beam}\\right)\ extrm{pb}, $$\\end{document}where the four uncertainties reflect the limited size of the data sample, experimental and theoretical systematic effects, and imperfect knowledge of both the integrated luminosity and the LHC beam energy, giving a total uncertainty of 3.9%. The result is in agreement with theoretical quantum chromodynamic calculations at next-to-next-to-leading order in the strong coupling constant, including the resummation of next-to-next-to-leading logarithmic soft-gluon terms, and constrains the parton distribution functions of the proton at large Bjorken-x.

Measurement of the tbar{t} production cross-section and lepton differential distributions in emu dilepton events from pp collisions at sqrt{s}=13,text {TeV} with the ATLAS detector

The inclusive top quark pair (tbar{t}) production cross-section sigma _{tbar{t}} has been measured in proton–proton collisions at sqrt{s}=13,text {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 emu pair and b-tagged jets, the cross-section is measured to be: σtt¯=826.4±3.6(stat)±11.5(syst)±15.7(lumi)±1.9(beam)pb,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$\\begin{aligned} \\sigma _{t\\bar{t}} = 826.4 \\pm 3.6\\,\\mathrm {(stat)}\\ \\pm 11.5\\,\\mathrm {(syst)}\\ \\pm 15.7\\,\\mathrm {(lumi)}\\ \\pm 1.9\\,\\mathrm {(beam)}\\,\\mathrm {pb}, \\end{aligned}$$\\end{document}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},text {GeV}. It is also combined with measurements at sqrt{s}=7,text {TeV} and sqrt{s}=8,text {TeV} to derive ratios and double ratios of tbar{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.

αs from top-quark pair production at hadron colliders

The strong coupling constant αs(MZ) is determined using inclusive top-quark pair production cross section measurements performed at the LHC and at the Tevatron. Individual values of αs(MZ) are extracted from measurements of different experiments at several centre-of-mass energies, using QCD predictions complete in NNLO perturbation theory, supplemented with NNLL approximations to all orders, and suitable sets of parton distribution functions. These values are then combined using a likelyhood-based approach, with special emphasis on a consistent treatment of systemtic uncertainties and their correlations. The final combined result is αs(MZ)=0.1177−0.0036+0.0034.

Determination of the strong coupling constant alpha _s left( m_Z right) from measurements of the total cross section for top\u2013antitop-quark production

We present a determination of the strong coupling constant alpha _s left( m_Z right) using inclusive top-quark pair production cross section measurements performed at the LHC and at the Tevatron. Following a procedure first applied by the CMS Collaboration, we extract individual values of alpha _s left( m_Z right) from measurements by different experiments at several centre-of-mass energies, using QCD predictions complete in NNLO perturbation theory, supplemented with NNLL approximations to all orders, and suitable sets of parton distribution functions. The determinations are then combined using a likelihood-based approach, where special emphasis is put on a consistent treatment of theoretical uncertainties and of correlations between various sources of systematic uncertainties. Our final combined result is alpha _s left( m_Z right) =0.1177^{+0.0034{}}_{-0.0036{}}.

Top quark production measurements using the ATLAS detector at the LHC

A selection from the inclusive top-quark pair production and single top-quark production cross-section measurements in proton-proton collisions with the ATLAS detector at the Large Hadron Collider is presented, with data collected in 2012 and early 2015 at centre-of-mass energies of 8 TeV and 13 TeV, respectively.

Addendum to ‘Measurement of the $$t\bar{t}$$ t t ¯ production cross-section using $$e\mu $$ e μ events with b-tagged jets in pp collisions at $$\sqrt{s}$$ s = 7 and 8 $$\,\mathrm{TeV}$$ TeV with the ATLAS detector’

The inclusive top quark pair ($t\bar{t}$) production cross-section $\sigma_{t\bar{t}}$ has been measured in $pp$ collisions at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV with the ATLAS experiment at the LHC, using $t\bar{t}$ events with an opposite-charge $e\mu$ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb$^{-1}$ and the 2012 8 TeV dataset of 20.3 fb$^{-1}$. The cross-section was measured to be: $\sigma_{t\bar{t}}=182.9\pm 3.1\pm 4.2\pm 3.6 \pm 3.3$ pb ($\sqrt{s}=7$ TeV) and $\sigma_{t\bar{t}}=242.9\pm 1.7\pm 5.5\pm 5.1\pm 4.2$ pb ($\sqrt{s}=8$ TeV, updated as described in the Addendum), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically-predicted cross-section on $m_t^{\rm pole}$, giving a result of $m_t^{\rm pole}=172.9^{+2.5}_{-2.6}$ GeV. By looking for an excess of $t\bar{t}$ production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks $\tilde{t}_1$ with masses close to the top quark mass decaying via $\tilde{t}_1\rightarrow t\tilde{\chi}^0_1$ to predominantly right-handed top quarks and a light neutralino $\tilde{\chi}_0^1$, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95% confidence level.

Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at s=13TeV with the ATLAS detector

his paper describes a measurement of the inclusive top quark pair production cross-section (sigma(t (t) over bar)) with a data sample of 3.2 fb(-1) of proton-proton collisions at a centre-of-mass e ...

Top quark pair production cross section using the ATLAS detector at the LHC

Measurements of the inclusive top quark pair production cross sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider are presented. The measurements are performed requiring one or two electrons or muons in the final state. Various experimental techniques are compared. The most accurate result in obtained requiring opposite sign electrons and muons, achieves a precision of a few percent, and is in good agreement with a recent NNLO+NNLL QCD calculation. In addition, a differential measurement of the top transverse momentum and kinematic properties of the top pair system are presented. This measurement requires one electron or muon in the final state and probes our understanding of top pair production in the TeV regime and is compared to recent Monte Carlo generators and theory calculations.

Measurement of the [Formula: see text] production cross-section using [Formula: see text] events with [Formula: see text]-tagged jets in [Formula: see text] collisions at [Formula: see text] and 8TeV with the ATLAS detector.

The inclusive top quark pair (toverline{t}) production cross-section {sigma _{toverline{t}}} has been measured in proton–proton collisions at {sqrt{s}=7~mathrm{TeV}} and {sqrt{s}=8~mathrm{TeV}} with the ATLAS experiment at the LHC, using toverline{t} events with an opposite-charge emu pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 {mathrm{fb}^{-1}} and the 2012 8 TeV dataset of 20.3 {mathrm{fb}^{-1}}. The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine {sigma _{toverline{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 was measured to be: \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} {\\sigma _{t\\overline{t}}}&= 182.9\\pm 3.1\\pm 4.2\\pm 3.6\\pm 3.3~\\mathrm{pb}\\ ({\\sqrt{s}=7~\\mathrm{TeV}})\\quad \\mathrm{and} \\\\ {\\sigma _{t\\overline{t}}}&= 242.4\\pm 1.7\\pm 5.5\\pm 7.5\\pm 4.2~\\mathrm{pb}\\ ({\\sqrt{s}=8~\\mathrm{TeV}}), \\end{aligned}$$\\end{document}σtt¯=182.9±3.1±4.2±3.6±3.3pb(s=7TeV)andσtt¯=242.4±1.7±5.5±7.5±4.2pb(s=8TeV),where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on {m}_{t}^mathrm{pole} giving a result of {m}_{t}^mathrm{pole} =172.9^{+2.5}_{-2.6} GeV. By looking for an excess of toverline{t} production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks {tilde{t}_{1}} with masses close to the top quark mass, decaying via {tilde{t}_{1}}rightarrow t{tilde{chi }_{1}^{0}} to predominantly right-handed top quarks and a light neutralino tilde{chi }_{1}^{0}, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.

Combination of measurements of the top-quark pair production cross section from the Tevatron Collider

We combine six measurements of the inclusive top-quark pair (ttbar) production cross section (sigma_ttbar) from data collected with the CDF and D0 detectors at the Fermilab Tevatron with proton anti-proton collisions at sqrt{s} = 1.96 TeV. The data correspond to integrated luminosities of up to 8.8 fb^{-1}. We obtain a value of sigma_ttbar = 7.60 \pm 0.41 pb for a top-quark mass of m_t=172.5 GeV. The contributions to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from systematic sources, and 0.21 pb from the uncertainty on the integrated luminosity. The result is in good agreement with the standard model expectation of 7.35^{+0.28}_{-0.33} pb at NNLO+NNLL in pertubative QCD.

Top quark pair production cross section with the ATLAS experiment

This document reviews the existing results of inclusive top quark pair production cross section measurements in proton-proton collisions at a center of mass energies of 7 and 8 TeV performed with the ATLAS detector at the Large Hadron Collider. These measurements cover the different analysis channels, single lepton, dilepton and all hadronic channel, as well as dedicated analysis for channels including tau leptons decaying hadronically. All measurements shown in this document are in good agreement with the Standard Model expectation.

Measurements of top quark pair relative differential cross-sections with ATLAS in pp collisions at $\sqrt{s} = 7\ \mbox{TeV}$

Measurements are presented of differential cross-sections for top quark pair production in pp collisions at sqrt(s) = 7 TeV relative to the total inclusive top quark pair production cross-section. A data sample of 2.05/fb recorded by the ATLAS detector at the Large Hadron Collider is used. Relative differential cross-sections are derived as a function of the invariant mass, the transverse momentum and the rapidity of the top quark pair system. Events are selected in the lepton (electron or muon) + jets channel. The background-subtracted differential distributions are corrected for detector effects, normalized to the total inclusive top quark pair production cross-section and compared to theoretical predictions. The measurement uncertainties range typically between 10% and 20% and are generally dominated by systematic effects. No significant deviations from the Standard Model expectations are observed.

Top pair production at CMS (includes charge asymmetry and ttbar resonance)

Measurements of top quark pair production are presented based on data recorded with the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) in 2011 and 2012. Inclusive and differential top quark pair production cross section measurements in various channels are described. Inclusive as well as differential measurements of the charge asymmetry in top quark pair events are summarised and a method for the extraction of the strong coupling alpha(s) from the measured top pair production cross section is discussed. All measurements are in agreement with the Standard Model predictions.

Inclusive top-pair production phenomenology with TOPIXS

We discuss various aspects of inclusive top-quark pair production based on TOPIXS, a new, flexible program that computes the production cross section at the Tevatron and LHC at next-to-next-to-leading logarithmic accuracy in soft and Coulomb resummation, including bound-state effects and the complete next-to-next-to-leading order result in the q-qbar channel, which has recently become available. We present the calculation of the top-pair cross section in pp collisions at 8 TeV centre-of-mass energy, as well as the cross sections for hypothetical heavy quarks in extensions of the standard model. The dependence on the parton distribution input is studied. Further we investigate the impact of LHC top cross section measurements at sqrt(s)=7 TeV on global fits of the gluon distribution using the NNPDF re-weighting method.

Phenomenology of [formula omitted]-factorization for inclusive top quark pair production at hadron colliders

We investigate the inclusive top quark pair production in proton–proton and proton–antiproton collisions at high energies in the framework of kT-factorization QCD approach. Our study is based on the off-shell partonic subprocesses g⁎g⁎→QQ¯ and q⁎q¯⁎→QQ¯, where the transverse momentum of both incoming quarks and gluons are taken into account. The unintegrated parton densities in a proton are determined by the Kimber–Martin–Ryskin prescription as well as the CCFM evolution equation. The conservative error analysis is performed and comparison with the results of traditional NLO pQCD calculations is done. Our predictions agree well with the recent experimental data taken by the D0, CDF, CMS and ATLAS Collaborations at the Tevatron and LHC energies.

Measurement of the top quark pair production cross section in thelepton+jetschannel in proton-antiproton collisions ats=1.96 TeV

We present a measurement of the inclusive top quark pair production cross section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data corresponding to an integrated luminosity of \lumi\ collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-$p_{T}$ isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of \ttbar events, the second using $b$-jet identification, and the third using both techniques to separate \ttbar\ signal from background. In the third case, we determine simultaneously the $t\bar{t}$ cross section and the ratio of the production rates of $W$+heavy flavor jets and $W$+light flavor jets, which reduces the impact of the systematic uncertainties related to the background estimation. Assuming a top quark mass of 172.5 GeV, we obtain $\sigma_{t\bar{t}} = 7.78^{+0.77}_{-0.64} $ pb. This result agrees with predictions of the standard model.

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at $\sqrt{s}=7$ TeV

A measurement of the production cross-section for top quark pairs($\ttbar$) in $pp$ collisions at $\sqrt{s}=7 \TeV$ is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\mu\mu$ or $e\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-$\ttbar$ Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM $\ttbar$ production. The inclusive top quark pair production cross-section is measured to be $\sigmattbar=145 \pm 31 ^{+42}_{-27}$ pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.

Th-P15:108 Regulation of the CD36 expression and cholesterol influx in THP-1 macrophage by PPAR

This paper describes a measurement of the inclusive top quark pair production cross-section (σtt¯) with a data sample of 3.2fb−1 of proton–proton collisions at a centre-of-mass energy of s=13TeV, 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 σtt¯ 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: 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.