Top Pair Production Cross Section Research Articles

First measurement of the top quark pair production cross section in proton-proton collisions at sqrt{s} = 13.6 TeV

The first measurement of the top quark pair ( textrm{t}overline{textrm{t}} ) production cross section in proton-proton collisions at sqrt{s} = 13.6 TeV is presented. Data recorded with the CMS detector at the CERN LHC in Summer 2022, corresponding to an integrated luminosity of 1.21 fb−1, are analyzed. Events are selected with one or two charged leptons (electrons or muons) and additional jets. A maximum likelihood fit is performed in event categories defined by the number and flavors of the leptons, the number of jets, and the number of jets identified as originating from b quarks. An inclusive textrm{t}overline{textrm{t}} production cross section of 881 ± 23 (stat + syst) ± 20 (lumi) pb is measured, in agreement with the standard model prediction of {924}_{-40}^{+32} pb.

Top cross section in the LHeC and FCC-he energy range

Predictions of the top-pair production cross section in electron-proton (ep) collisions at the future circular collider hadron-electron (FCC-he) and the large hadron electron collider (LHeC) in the leading order (LO) and the next-to-leading order (NLO) approximations in perturbative quantum chromodynamics (QCD) are presented. Numerical results for the top structure functions and the ratio of structure functions are computed at the renormalization scale μ2=Q2+4mt2 in the collinear generalized double asymptotic scaling (DAS) approach. These results are presented in terms of the effective parameters of the parameterization of F2(x,Q2), where relying on a Froissart-bounded. These quantitative results can be important for future collider experiments at the center-of-mass energy frontier and the improvement of the phenomenological models for the development of the cosmic ray cascades in ultra-high-energy domain. We obtained the uncertainties because of the power-law behavior x−Δ of the collinear parton distribution functions (PDFs), the factorization, and renormalization scales, on the top properties at high inelasticity for the FCC-he center-of-mass (CM) energy at the NLO approximation.

Measurement of the inclusive mathrm{t}overline{mathrm{t}} production cross section in proton-proton collisions at sqrt{s} = 5.02 TeV

The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb−1, is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of {66.8}_{-3.1}^{+2.9} pb.

Top-pair production via gluon fusion in the Standard Model effective field theory

We compute the leading corrections to the differential cross section for top-pair production via gluon fusion due to dimension-six operators at leading order in QCD. The Standard Model fields are assumed to couple only weakly to the hypothetical new sector. A systematic approach then suggests treating single insertions of the operator class containing gluon field strength tensors on the same footing as expli\-citly loop suppressed contributions from four-fermion operators. This is in particular the case for the chromomagnetic operator $Q_{(uG)}$ and the purely bosonic operators $Q_{(G)}$ and $Q_{(\varphi G)}$. All leading order dimension-six contributions are consequently suppressed with a loop factor $1/16\pi^2$.

Recent top quark measurements with the CMS experiment

Latest results on top quark pair and single top quark production cross sections (inclusive and differential) are presented using proton-proton collision data collected by CMS. The results are used to constrain the standard model parameters. For the first time, the third row of the CKM matrix is measured from single top quark events and multidifferential cross sections are used to constrain simultaneously the top quark pole mass, α S , and PDFs. Moreover, recent results on top quark properties, such as mass measurements or constraints on top Yukawa from differential cross sections are also presented.

Measurement of differential tt¯ production cross sections using top quarks at large transverse momenta in pp collisions at s=13 TeV

A measurement is reported of differential top quark pair ($\mathrm{t\bar{t}}$) production cross sections, where top quarks are produced at large transverse momenta. The data collected with the CMS detector at the LHC are from pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The measurement uses events where at least one top quark decays as t $\to$ Wb $\to$ qq'b and is reconstructed as a large-radius jet with transverse momentum in excess of 400 GeV. The second top quark is required to decay either in a similar way, or leptonically, as inferred from a reconstructed electron or muon, a bottom quark jet, and a missing transverse momentum due to the undetected neutrino. The cross section is extracted as a function of kinematic variables of individual top quarks or of the $\mathrm{t\bar{t}}$ system. The results are presented at the particle level, within a region of phase space close to that of the experimental acceptance, and at the parton level, and are compared to various theoretical models. In both decay channels the observed absolute cross sections are significantly lower than the predictions from theory, while the normalized differential measurements are well described.

Measurement of the top quark pair production cross section in dilepton final states containing one \u03c4 lepton in pp collisions at sqrt{s} = 13 TeV

The cross section of top quark pair production is measured in the mathrm{t}overline{mathrm{t}}to left(ell {nu}_{ell}right)left({uptau}_{mathrm{h}}{nu}_{uptau}right)mathrm{b}overline{mathrm{b}} final state, where τh refers to the hadronic decays of the τ lepton, and ℓ is either an electron or a muon. The data sample corresponds to an integrated luminosity of 35.9 fb−1 collected in proton-proton collisions at sqrt{s} = 13 TeV with the CMS detector. The measured cross section is {sigma}_{mathrm{t}overline{mathrm{t}}} = 781 ± 7 (stat) ± 62 (syst) ± 20 (lumi) pb, and the ratio of the partial width Γ(t → τντb) to the total decay width of the top quark is measured to be 0.1050 ± 0.0009 (stat) ± 0.0071 (syst). This is the first measurement of the mathrm{t}overline{mathrm{t}} production cross section in proton-proton collisions at sqrt{s} = 13 TeV that explicitly includes τ leptons. The ratio of the cross sections in the ℓτh and ℓℓ final states yields a value {R}_{ell {uptau}_{mathrm{h}}/mathcal{ll}} = 0.973 ± 0.009 (stat) ± 0.066 (syst), consistent with lepton universality.

Differential top quark pair production at the LHC: Challenges for PDF fits

We present the results of a PDF fit to differential top quark production within the MMHT framework. We in particular consider ATLAS data in the lepton + jet and dilepton channels and CMS data in the lepton + jet channel, at 8 TeV. While the fit quality to the ATLAS dilepton data is good, for the CMS case we see some issues in achieving a good fit quality for certain distributions. However, we focus on the ATLAS lepton + jet data, for which correlations of the statistical and systematic errors are provided across the four relevant distributions for PDF determination, namely p_T^t, M_{tt}, y_t and y_{tt}. We find severe difficulties in fitting these distributions simultaneously, with particular sensitivity to the precise degree of correlation taken between the dominant two-point MC uncertainties in the data. We investigate the effect of some reasonable decorrelation of these uncertainties, finding the impact on the fit quality to be significant and the resultant gluon not negligible. This is in particular found to be larger than the effect of including NNLO QCD and NLO EW corrections in the top quark pair production cross section on the fit, motivating a closer understanding of the physics underlying these errors sources and in particular the uncertainty on the degree of correlation in them.

Search for supersymmetry in events with a photon, jets, mathrm {b}-jets, and missing transverse momentum in proton\u2013proton collisions at 13,text {Te}text {V}

A search for supersymmetry is presented based on events with at least one photon, jets, and large missing transverse momentum produced in proton–proton collisions at a center-of-mass energy of 13,text {Te}text {V}. The data correspond to an integrated luminosity of 35.9,text {fb}^{-1} and were recorded at the LHC with the CMS detector in 2016. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of mathrm {b}-tagged jets, and the missing transverse momentum. No significant excess of events is observed with respect to the expectations from standard model processes. Limits are placed on the gluino and top squark pair production cross sections using several simplified models of supersymmetric particle production with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the next-to-lightest supersymmetric particle, the production of gluinos with masses as large as 2120,text {Ge}text {V} and the production of top squarks with masses as large as 1230,text {Ge}text {V} are excluded at 95% confidence level.

Magnifying the ATLAS stealth stop splinter: impact of spin correlations and finite widths

In this paper, we recast a “stealth stop” search in the notoriously difficult region of the stop-neutralino Simplified Model parameter space for which mleft({tilde{t}}_1right)-mleft({tilde{upchi}}_1^0right)simeq {m}_t . The properties of the final state are nearly identical for tops and stops, while the rate for stop pair production is mathcal{O} (10%) of that for toverline{t} . Stop searches away from this stealth region have left behind a “splinter” of open parameter space when mleft({tilde{t}}_1right)simeq {m}_t . Removing this splinter requires surgical precision: the ATLAS constraint on stop pair production reinterpreted here treats the signal as a contaminant to the measurement of the top pair production cross section using data from sqrt{s}=7 TeV and 8 TeV in a correlated way to control for some systematic errors. ATLAS fixed mleft({tilde{t}}_1right)simeq {m}_tkern0.5em andkern0.5em mleft({tilde{upchi}}_1^0right)=1 GeV, implying that a careful recasting of these results into the full mleft({tilde{t}}_1right)-mleft({tilde{upchi}}_1^0right) plane is warranted. We find that the parameter space with mleft({tilde{upchi}}_1^0right)lesssim 55 GeV is excluded for mleft({tilde{t}}_1right)simeq {m}_t — although this search does cover new parameter space, it is unable to fully pull the splinter. Along the way, we review a variety of interesting physical issues in detail: (i) when the two-body width is a good approximation; (ii) how assuming the narrow width approximation affects the total rate; (iii ) how the production rate is affected when the wrong widths are used; (iv ) what role propagating the spin correlations consistently through the multi-body decay chain plays in the limits. In addition, we provide a guide to using MadGraph for implementing the full production including finite width and spin correlation effects, and we survey a variety of pitfalls one might encounter.

Measurement of the inclusive mathrm{t}overline{mathrm{t}} cross section in pp collisions at sqrt{s}=5.02 TeV using final states with at least one charged lepton

The top quark pair production cross section left({sigma}_{mathrm{t}overline{mathrm{t}}}right) is measured for the first time in pp collisions at a center-of-mass energy of 5.02 TeV. The data were collected by the CMS experiment at the LHC and correspond to an integrated luminosity of 27.4 pb−1. The measurement is performed by analyzing events with at least one charged lepton. The measured cross section is {sigma}_{mathrm{t}overline{mathrm{t}}} = 69.5 ± 6.1 (stat) ± 5.6 (syst) ± 1.6 (lumi) pb, with a total relative uncertainty of 12%. The result is in agreement with the expectation from the standard model. The impact of the presented measurement on the determination of the gluon distribution function is investigated.

Search for direct production of supersymmetric partners of the top quark in the all-jets final state in proton-proton collisions at sqrt{s}=13 TeV

A search for direct production of top squark pairs in events with jets and large transverse momentum imbalance is presented. The data are based on proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector in 2016 at the CERN LHC, and correspond to an integrated luminosity of 35.9 fb−1. The search considers a variety of R-parity conserving supersymmetric models, including ones for which the top squark and neutralino masses are nearly degenerate. Specialized jet reconstruction tools are developed to exploit the unique characteristics of the signal topologies. With no significant excess of events observed above the standard model expectations, upper limits are set on the direct top squark pair production cross section in the context of simplified supersymmetric models for various decay hypotheses. Models with larger differences in mass between the top squark and neutralino are probed for masses up to 1040 and 500 GeV, respectively, whereas models with a more compressed mass hierarchy are probed up to 660 and 610 GeV, respectively. The smallest mass difference probed is for masses near to 550 and 540 GeV, respectively.

αs from the top quark pair production cross section

Five measurements of the top quark pair production cross section from hadron colliders are compared with the theoretical prediction (up the next-to-next-to-leading order in QCD) in order to determine the strong coupling constant αs. The determination is performed for several PDF sets. The individual determinations of αs are combined to form a single best estimate using the Best Linear Unbiased Estimate (BLUE) procedure. Preliminary combined results indicate a higher value of αs than that determined in a previous extraction of αs from the top quark pair production cross section.

Measurements of the mathrm{t}overline{mathrm{t}} production cross section in lepton+jets final states in pp collisions at 8 ,text {TeV} and ratio of 8 to 7\xa0,text {TeV} cross sections

A measurement of the top quark pair production (mathrm{t}overline{mathrm{t}} ) cross section in proton–proton collisions at the centre-of-mass energy of 8,text {TeV} is presented using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.6,text {fb}^{-text {1}}. This analysis is performed in the mathrm{t}overline{mathrm{t}} decay channels with one isolated, high transverse momentum electron or muon and at least four jets, at least one of which is required to be identified as originating from hadronization of a b quark. The calibration of the jet energy scale and the efficiency of b jet identification are determined from data. The measured mathrm{t}overline{mathrm{t}} cross section is 228.5 pm 3.8,text {(stat)} pm 13.7,text {(syst)} pm 6.0,text {(lumi)} text { pb} . This measurement is compared with an analysis of 7,text {TeV} data, corresponding to an integrated luminosity of 5.0,text {fb}^{-text {1}}, to determine the ratio of 8,text {TeV} to 7,text {TeV} cross sections, which is found to be 1.43 pm 0.04,text {(stat)} pm 0.07,text {(syst)} pm 0.05,text {(lumi)} . The measurements are in agreement with QCD predictions up to next-to-next-to-leading order.

Highlights of top quark cross-section measurements at ATLAS

The highlights of the measurements of top quark production in proton-proton collisions at the Large Hadron Collider with the ATLAS detector are presented. The inclusive measurements of the top-pair production cross section have reached high precision and are compared to the best available theoretical calculations. The differential cross section measurements, including results using boosted top quarks, probe our understanding of top-pair production in the TeV regime. The results are compared to Monte Carlo generators implementing LO and NLO matrix elements matched with parton showers. Measurements of the single top quark production cross section are presented in the t -channel and s -channel, and with associated production with a W boson. For the t -channel production, results on the ratio between top quark and antitop quark production cross sections and differential measurements are also included.

Measurement of the inclusivett¯production cross section inpp¯collisions ats=1.96 TeVand determination of the top quark pole mass

The inclusive cross section of top quark-antiquark pairs produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is measured in the lepton$+$jets and dilepton decay channels. The data sample corresponds to 9.7 fb${}^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Employing multivariate analysis techniques we measure the cross section in the two decay channels and we perform a combined cross section measurement. For a top quark mass of 172.5 GeV, we measure a combined inclusive top quark-antiquark pair production cross section of $\sigma_{t\bar{t}} = 7.26 \pm 0.13\,(\mathrm{stat.})\,^{+0.57}_{-0.50}\,(\mathrm{syst.})$ pb which is consistent with standard model predictions. We also perform a likelihood fit to the measured and predicted top quark mass dependence of the inclusive cross section, which yields a measurement of the pole mass of the top quark. The extracted value is $m_t = 172.8 \pm 1.1\,(\mathrm{theo.})\,^{+3.3}_{-3.1}\,(\mathrm{exp.})$ GeV.

Threshold singularities, dispersion relations and fixed-order perturbative calculations

We show how to correctly treat threshold singularities in fixed-order perturbative calculations of the electron anomalous magnetic moment and hadronic pair production processes such as top pair production. With respect to the former, we demonstrate the equivalence of the "non-perturbative", resummed treatment of the vacuum polarization contribution, whose spectral function exhibits bound state poles, with the fixed-order calculation by identifying a threshold localized term in the four-loop spectral function. In general, we find that a modification of the dispersion relation by threshold subtractions is required to make fixed-order calculations well-defined and provide the subtraction term. We then solve the apparent problem of a divergent convolution of the partonic cross section with the parton luminosity in the computation of the top pair production cross section starting from the fourth-order correction. We find that when the computation is performed in the usual way as an integral of real and virtual corrections over phase space at a given order in the expansion in the strong coupling, an additional contribution has to be added at N3LO.

Search for R-parity violating decays of a top squark in proton–proton collisions at s=8 TeV

The results of a search for a supersymmetric partner of the top quark (top squark), pair-produced in proton-proton collisions at sqrt(s) = 8 TeV, are presented. The search, which focuses on R-parity violating, chargino-mediated decays of the top squark, is performed in final states with low missing transverse momentum, two oppositely charged electrons or muons, and at least five jets. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 inverse femtobarns collected with the CMS detector at the LHC in 2012. The data are found to be in agreement with the standard model expectation, and upper limits are placed on the top squark pair production cross section at 95% confidence level. Assuming a 100% branching fraction for the top squark decay chain, top squark to t + chargino, chargino to lepton + jj, top squark masses less than 890 (1000) GeV for the electron (muon) channel are excluded for the first time in models with a single nonzero R-parity violating coupling lambda'[ijk] (i,j,k <= 2), where i,j,k correspond to the three generations.

Recent top physics highlights at the LHC

Recent highlights of measurements by the ATLAS and CMS collaborations involving top quarks produced at the LHC are presented. Emphasis is put on precise inclusive and differential top pair production cross section measurements and comparisons to QCD calculations. Special attention is given to fiducial measurements. Results on electroweak single top quarks production and the recent evidence of top pair produced in associated with vector bosons are summarised. The experimental status of top quark mass measurements is critically reviewed.

Top quark pair production and top quark properties at CDF

We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into b-quarks, performed by measuring the ratio R between the top quark branching fraction to b-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element |Vtb| from the ratio R is discussed. We also present the latest measurements on the forward-backward asymmetry (AFB) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in tt‾ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.