Measurement of Top Quark Polarization in Top-Antitop Events from Proton-Proton Collisions at √s=7 TeV Using the ATLAS Detector

This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4.7 fb-1 of proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at √s=7 TeV. Final states containing one or two isolated leptons (electrons or muons) and jets are considered. Two measurements of alfaP, the product of the leptonic spin-analyzing power and the top quark polarization, are performed assuming that the polarization is introduced by either a CP conserving or a maximally CP violating production process. The measurements obtained, alfaPCPC =-0:035+- 0.014(stat)+- 0.037(syst) and alfaPCPV = 0.020+- 0.016(stat)+0.013-0.017(syst), are in good agreement with the standard model prediction of negligible top quark polarization.