2012/03/01 by Soualah, Rachik
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)
paper · doi:10.48550/arxiv.1203.0149
We present a measurement of the charge asymmetry in top-antitop production using data corresponding to an integrated luminosity of 0.70 fb-1 of proton-proton collisions at √ s = 7 TeV collected by the ATLAS detector. The top pair events decaying semileptonically (lepton+jets channel) to either an electron or muon, missing transverse energy and at least four jets are selected. The reconstruction of the tt events was performed using a kinematic likelihood approach. The difference of absolute values of top and antitop rapidities is used to define the charge asymmetry: AC = (N(|ΔY|>0) - N(|ΔY|<0)) / (N(|ΔY>0) + N(|ΔY|<0)). To allow comparisons with theory calculations, a Bayesian unfolding technique is applied to correct the measured |ΔY| distributions for acceptance and detector effects. The top charge asymmetry in both channels (e and mu) after correction is measured to be: AC = -0.009 ± 0.023 (stat) ± 0.032 (syst) (e+jets channel) and AC = -0.028 ± 0.019 (stat) ± 0.022 (syst) (μ+jets channel) giving a combined result of : AC = -0.024 ± 0.016 (stat) ± 0.023 (syst). These results are compatible with the Standard Model predictions of AC=0.006.