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Measurement of the W boson polarization in top decay at CDF at s√=1.8  TeV

CollaborationWith : Clark, Allan Geoffrey / D'Onofrio, Monica / Wu, Xin
Published in Physical Review. D. 2005, vol. 71, no. 03, p. 031101
Abstract The polarization of the W boson in t→Wb decay is unambiguously predicted by the standard model of electroweak interactions and is a powerful test of our understanding of the tbW vertex. We measure this polarization from the invariant mass of the b quark from t→Wb and the lepton from W→lν whose momenta measure the W decay angle and direction of motion, respectively. In this paper we present a measurement of the decay rate (fV+A) of the W produced from the decay of the top quark in the hypothesis of V+A structure of the tWb vertex. We find no evidence for the nonstandard V+A vertex and set a limit on fV+A < 0.80 at 95% confidence level. By combining this result with a complementary observable in the same data, we assign a limit on fV+A < 0.61 at 95% CL. This corresponds to a constraint on the right-handed helicity component of the W polarization of f+<0.18 at 95% CL. This limit is the first significant direct constraint on fV+A in top decay.
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CDF COLLABORATION. Measurement of the W boson polarization in top decay at CDF at s√=1.8  TeV. In: Physical Review. D, 2005, vol. 71, n° 03, p. 031101. https://archive-ouverte.unige.ch/unige:38287

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Deposited on : 2014-06-30

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