Measurement of lepton differential distributions and the top quark mass in t t ̄ production in pp collisions at √s = 8 TeV with the ATLAS detector

Abstract

This paper presents single lepton and dilepton kinematic distributions measured in dileptonic tt ̄ events produced in 20.2 fb−1 of √s = 8 TeV pp collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge eμ pair and one or two b-tagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of mpole = 173.2 ± 0.9 ± 0.8 ± 1.2 GeV, where the three uncertainties t arise from data statistics, experimental systematics, and theoretical sources.