UC Santa Cruz

This paper presents a measurement of the top quark pair ($$ t\overline{t} $$) production charge asymmetry AC using 4.7 fb−1 of proton-proton collisions at a centre-of-mass energy $$ \sqrt{s} $$ = 7 TeV collected by the ATLAS detector at the LHC. A $$ t\overline{t} $$-enriched sample of events with a single lepton (electron or muon), missing transverse momentum and at least four high transverse momentum jets, of which at least one is tagged as coming from a b-quark, is selected. A likelihood fit is used to reconstruct the $$ t\overline{t} $$ event kinematics. A Bayesian unfolding procedure is employed to estimate AC at the parton-level. The measured value of the $$ t\overline{t} $$ production charge asymmetry is AC = 0.006 ± 0.010, where the uncertainty includes both the statistical and the systematic components. Differential AC measurements as a function of the invariant mass, the rapidity and the transverse momentum of the $$ t\overline{t} $$ system are also presented. In addition, AC is measured for a subset of events with large $$ t\overline{t} $$ velocity, where physics beyond the Standard Model could contribute. All measurements are consistent with the Standard Model predictions.