Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production

Abstract : We present measurements of lepton (l) angular distributions in ttbar -> W+ b W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4fb^-1, collected with the D0 detector at the Fermilab Collider, we find that the angular distributions of l- relative to anti-protons and l+ relative to protons are in agreement with each other. Combining the two distributions and correcting for detector acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat) +- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted) = (4.7 +- 0.1)%. This result is further combined with the measurement based on the analysis of the l+jets final state to obtain A^l_FB = (11.8 +- 3.2)%. Furthermore, we present a first study of the top-quark polarization.
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Contributor : Vernay Emmanuelle <>
Submitted on : Tuesday, July 3, 2012 - 8:00:35 AM
Last modification on : Tuesday, July 3, 2012 - 8:00:35 AM

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V.M. Abazov, H. Li, G. Sajot, J. Stark, S. Greder, et al.. Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production. Physical Review D, American Physical Society, 2013, 87, pp.011103(R). <10.1103/PhysRevD.87.011103>. <in2p3-00713888>

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