Measurement of the tt production cross-section and lepton differential distributions in e mu dilepton events from pp collisions at root s=13 TeV with the ATLAS detector

Abstract

The inclusive top quark pair (tt<overbar></mml:mover>) production cross-section sigma tt<overbar></mml:mover> has been measured in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13<mml:mspace width=0.166667em></mml:mspace>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: <disp-formula id=Equ10><mml:mtable><mml:mtr><mml:mtd columnalign=right>sigma tt<overbar></mml:mover>=826.4 +/- 3.6<mml:mspace width=0.166667em></mml:mspace>(stat)<mml:mspace width=4pt></mml:mspace>+/- 11.5<mml:mspace width=0.166667em></mml:mspace>(syst)<mml:mspace width=4pt></mml:mspace>+/- 15.7<mml:mspace width=0.166667em></mml:mspace>(lumi)<mml:mspace width=4pt></mml:mspace>+/- 1.9<mml:mspace width=0.166667em></mml:mspace>(beam)<mml:mspace width=0.166667em></mml:mspace>pb,</mml:mtd></mml:mtr></mml:mtable><graphic xmlns:xlink=http://www.w3.org/1999/xlink xlink:href=10052_2020_7907_Article_Equ10.gif position=anchor></graphic></disp-formula>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 mtpole, giving mtpole=173.1-2.1+2.0<mml:mspace width=0.166667em></mml:mspace>GeV. It is also combined with measurements at <mml:msqrt>s</mml:msqrt><mml:mo>=7<mml:mspace width=0.166667em></mml:mspace>TeV and <mml:msqrt>s</mml:msqrt><mml:mo>=8<mml:mspace width=0.166667em></mml:mspace>TeV to derive ratios and double ratios of t<mml:mover accent=true>t<mml:mo stretchy=false><overbar></mml:mover> 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.