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

• Autor(a) principal: Castro, Nuno Filipe
• Data de Publicação: 2013
• Outros Autores: Onofre, A., ATLAS Collaboration
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/1822/57577
• topic: Ciências Naturais::Ciências Físicas; Science & Technology

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 root s = 7 TeV. Final states containing one or two isolated leptons ( electrons or muons) and jets are considered. Two measurements of alpha P-l, 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, alpha P-l(CPC) = -0: 035 +/- 0: 014(stat) +/- 0: 037(syst) and alpha P-l(CPV) = 0: 020 +/- 0: 016(stat)(-0.017)(+0.013)(syst), are in good agreement with the standard model prediction of negligible top quark polarization.