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

Abstract

The inclusive top quark pair (tt) production cross-section σ tt has been measured in proton-proton collisions at √ 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 eμ pair and b-tagged jets, the cross-section is measured to be: σ tt = 826.4 ± 3.6 (stat) ± 11.5 (syst) ± 15.7 (lumi) ±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 pole t , giving m pole t = 173.1 +2.0 −2.1 GeV. It is also combined with measurements at √ s = 7 TeV and √ s = 8 TeV to derive ratios and double ratios of tt and Z cross-sections at different energies. The same event sample is used to measure absolute and normalised differential cross-sections as functions of singlelepton and dilepton kinematic variables, and the results are compared with predictions from various Monte Carlo event generators.

Top quark pair production in the exclusive processes at the LHC

“…As the inclusive tt data are quite well described by predictions derived using these equations (see, e.g., Ref. [7]) and the results presented in Ref. [26] indicate that the uncertainty on g P is small in that kinematical range, we expect, as well, a small impact on our predictions associated with the choice of the diffractive parton distribution.…”

“…This expectation is directly related to the fact that the top quark couples to all gauge bosons and the Higgs boson, which implies that the top production is very sensitive to the presence of BSM phenomena. In addition, recent experimental results for the inclusive top pair production have demonstrated that this process can be used to measure the top mass in a well-defined scheme with high accuracy [5][6][7][8][9][10]. These results provide motivation for the study of the top pair production in diffractive processes, where the final state is cleaner than the typical inclusive one, where both incident protons fragment and a large number of particles are produced in addition to the top pair (for a review on diffraction see, e.g., Ref.…”

NNLO QCD corrections to leptonic observables in top-quark pair production and decay

“…In this section we compare predictions for one-and two-dimensional leptonic differential distributions based on inclusive selection (in the sense of section 3) with ATLAS measurements [67]. The fiducial phase-space of the ATLAS analysis has only lepton requirements and no explicit cuts on jets.…”

“…The fiducial phase-space of the ATLAS analysis has only lepton requirements and no explicit cuts on jets. Two different measurements are presented in the ATLAS publication [67]: one that includes top-quark decays into τ -leptons and one which does not. In this work we do not consider decays to τ leptons and therefore exclusively compare to the τ -less measurement.…”

Measurements of top-quark pair single- and double-differential cross-sections in the all-hadronic channel in pp collisions at $$ \sqrt{\mathrm{s}} $$ = 13 TeV using the ATLAS detector

“…The measurements of these observables allow better understanding of correlations between different aspects of the tt system kinematics. These combinations are useful for extracting information about PDFs and measuring the top-quark pole mass from the differential cross-section measurements [78,79]. The combinations considered are:…”