Measurement of the $t\overline{t}$ production cross-section and lepton differential distributions in $e\mu $ dilepton events from pp collisions at $\sqrt{s}=13\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ with the ATLAS detector

The inclusive top quark pair ( $t\overline{t}$ ) production cross-section ${\sigma }_{t\overline{t}}$ has been measured in proton–proton collisions at $\sqrt{s}=13\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ , using 36.1 fb ${}^{-1}$ of data collected in 2015–2016 by the ATLAS experiment at the LHC. Using events with an opposite-charge $e\mu $ pair and b-tagged jets, the cross-section is measured to be: $\begin{array}{c}{\sigma }_{t\overline{t}}=826.4±3.6\phantom{\rule{0.166667em}{0ex}}\left(\mathrm{stat}\right)\phantom{\rule{4pt}{0ex}}±11.5\phantom{\rule{0.166667em}{0ex}}\left(\mathrm{syst}\right)\phantom{\rule{4pt}{0ex}}±15.7\phantom{\rule{0.166667em}{0ex}}\left(\mathrm{lumi}\right)\phantom{\rule{4pt}{0ex}}±1.9\phantom{\rule{0.166667em}{0ex}}\left(\mathrm{beam}\right)\phantom{\rule{0.166667em}{0ex}}\mathrm{pb},\end{array}$ 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 ${m}_{t}^{\mathrm{pole}}$ , giving ${m}_{t}^{\mathrm{pole}}=173.{1}_{-2.1}^{+2.0}\phantom{\rule{0.166667em}{0ex}}\text{GeV}$ . It is also combined with measurements at $\sqrt{s}=7\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ and $\sqrt{s}=8\phantom{\rule{0.166667em}{0ex}}\text{TeV}$ to derive ratios and double ratios of $t\overline{t}$ and Z cross-sections at different energies. The same event sample is used to measure absolute and normalised differential cross-sections as functions of single-lepton and dilepton kinematic variables, and the results are compared with predictions from various Monte Carlo event generators.