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

This note 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 $\sqrt{s} = 7$ 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 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 charge asymmetry is 0.006 $\pm$ 0.010 (stat. + syst.). 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 performed. 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.