Measurement of the charge asymmetry in the top-quark dilepton decay channel in pp collision data at $\sqrt{s}$ = 7 TeV using the ATLAS detector

A measurement of the top-quark pair charge asymmetry in the dileptonic decay channel is presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 4.7 fb^-1 of proton-proton collision data at √s = 7 TeV recorded by the ATLAS detector. The event selection requires exactly two high energetic charged leptons (electrons or muons), large missing transverse energy and a minimum of two jets. The kinematic system of the initial top-quark pair is reconstructed using the Kinematic Likelihood Fitter. This thesis focuses on the calculation of the central charge asymmetry A_C, as an observable for the top-quark pair charge asymmetry. Iterative Bayesian unfolding is applied to correct for acceptance and detector resolution effects on the observable and to obtain the value of A_C at parton level. The central asymmetry after application of the unfolding procedure and combination of the three possible dileptonic decay channels is measured to be A_C = 0.055 +/- 0.041 (stat.) +/- 0.029 (syst.), for an event selection with at least one jet to be tagged by a heavy flavour tagging algorithm. The value is consistent with the Standard model prediction (at √s = 7 TeV) of A_C^(theory) = 0.0123 +/- 0.0005.