Measurement of the Top Quark Pair Production Charge Asymmetry in Proton-Proton Collisions at √s̅ = 7 TeV Using the ATLAS Detector

Abstract

This paper presents a measurement of the top quark pair (tt̅) production charge asymmetry A_C using 4.7 fb−1 of proton-proton collisions at a centre-of-mass energy √s̅ = 7 TeV collected by the ATLAS detector at the LHC. A tt̅ -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 tt̅ event kinematics. A Bayesian unfolding procedure is employed to estimate A_C at the parton-level. The measured value of the tt̅ 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 tt̅ system are also presented. In addition, A_C is measured for a subset of events with large tt̅ velocity, where physics beyond the Standard Model could contribute. All measurements are consistent with the Standard Model predictions.