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-->lnu whose momenta measure the W decay angle and direction of motion, respectively. In this paper we present a measurement of the decay rate (f(V+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 f(V+A) < 0.80 at 95% confidence level. By combining this result with a complementary observable in the same data, we assign a limit on f(V+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 f(V+A) in top decay.

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

INTROZZI, GIANLUCA;
2005-01-01

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-->lnu whose momenta measure the W decay angle and direction of motion, respectively. In this paper we present a measurement of the decay rate (f(V+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 f(V+A) < 0.80 at 95% confidence level. By combining this result with a complementary observable in the same data, we assign a limit on f(V+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 f(V+A) in top decay.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11571/577422
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