UC Irvine

Differential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs (tt¯$$ t\overline{t} $$) 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 s$$ \sqrt{s} $$ = 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 tt¯$$ t\overline{t} $$ 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,$$ {\sigma}_{t\overline{t}}=829\pm 1\ \left(\textrm{stat}\right)\pm 13\ \left(\textrm{syst}\right)\pm 8\ \left(\textrm{lumi}\right)\pm 2\ \left(\textrm{beam}\right)\ \textrm{pb}, $$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.