Measurement of top quark polarization in top-antitop events from proton-proton collisions at √s=7 TeV using the ATLAS detector. Physical Review Letters Volume 111, Issue 23, 4 December 2013, Article number 232002

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 αℓP, 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, αℓPCPC=-0.035±0. 014(stat)±0.037(syst) and αℓPCPV=0. 020±0.016(stat)-0.017 0.013(syst), are in good agreement with the standard model prediction of negligible top quark polarization.
Indexed keywords
ATLAS detectors; Final state; Large Hadron Collider; Measurements of; Production process; Proton proton collisions; The standard model; Top quarks