Precise measurement of the t tbar production cross-section and lepton differential distributions in e mu dilepton events from root s = 13 TeV pp collisions with the ATLAS detector

The inclusive top quark pair (t tbar) cross-section sigma(t tbar) has been measured in proton–proton collisions at root s = 13 TeV, using 140 fb-1 of data collected by the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge eμ pair and b-tagged jets, the cross section is measured to be: sigma(t tbar) = 829.3 +- 1.3 (stat) +- 8.0 (syst) +- 7.3 (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 proton beam energy, giving a total uncertainty of 1.3%. The result is used to determine the top quark pole mass via the dependence of the predicted cross-section on m_t^pole , giving m_t^pole = 172.8+1.5−1.7 GeV. The same event sample is used to measure absolute and normalised differential cross-sections for the t tbar -> e mu nu nubar b bbar process as a function of single-lepton and dilepton kinematic variables. Complementary measurements of e mu b bbar production, treating both t tbar and Wt events as signal, are also provided. Both sets of differential cross-sections are compared to the predictions of various Monte Carlo event generators, demonstrating that the state-of-the-art generators Powheg MiNNLO and Powheg bb4l describe the data better than Powheg hvq.