Measurements of top-quark pair differential cross-sections in the $$e\mu $$ e μ channel in pp collisions at $$\sqrt{s} = 13$$ s = 13  TeV using the ATLAS detector

Abstract

Abstract This article presents measurements of $$t\bar{t}$$ t t ¯ differential cross-sections in a fiducial phase-space region, using an integrated luminosity of 3.2 fb $$^{-1}$$ - 1 of proton–proton data at a centre-of-mass energy of $$\sqrt{s} = 13$$ s = 13 TeV recorded by the ATLAS experiment at the LHC in 2015. Differential cross-sections are measured as a function of the transverse momentum and absolute rapidity of the top quark, and of the transverse momentum, absolute rapidity and invariant mass of the $$t\bar{t}$$ t t ¯ system. The $$t\bar{t}$$ t t ¯ events are selected by requiring one electron and one muon of opposite electric charge, and at least two jets, one of which must be tagged as containing a b-hadron. The measured differential cross-sections are compared to predictions of next-to-leading order generators matched to parton showers and the measurements are found to be consistent with all models within the experimental uncertainties with the exception of the Powheg-Box $$+$$ + Herwig++ predictions, which differ significantly from the data in both the transverse momentum of the top quark and the mass of the $$t\bar{t}$$ t t ¯ system.