Abstract
The inclusive top quark pair (t (t) over bar) cross-section sigma(t (t) over bar) 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 e mu pair and b-tagged jets, the crosssection is measured to be: σ tt̄ = 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(-1.7)(+1.5) GeV. The same event sample is used to measure absolute and normalised differential cross-sections for the tt̄ -> e μ vv̄bb̄ process as a function of single-lepton and dilepton kinematic variables. Complementary measurements of e μ bb̄ production, treating both tt̄ 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.