Measurement of the top quark pair production charge asymmetry in proton-proton collisions at $\sqrt{s}$ = 7 TeV using the ATLAS detector

This paper presents a measurement of the top quark pair ($t\bar{t}$) production charge asymmetry $A_C$ using 4.7 fb−1 of proton-proton collisions at a centre-of-mass energy √s = 7 TeV collected by the ATLAS detector at the LHC. A $t\bar{t}$ 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 $t\bar{t}$ event kinematics. A Bayesian unfolding procedure is employed to estimate $A_C$ at the parton–level. The measured value of the $t\bar{t}$ production charge asymmetry is $A_C$ = 0.006± 0.010, where the uncertainty includes both the statistical and the systematic components. Differential $A_C$ measurements as a function of the invariant mass, the rapidity and the transverse momentum of the $t\bar{t}$-system are also presented. In addition, $A_C$ is measured for a subset of events with large $t\bar{t}$ velocity, where physics beyond the Standard Model could contribute. All measurements are consistent with the Standard Model predictions.