Measurement of the W boson polarization in top decay at CDF at root s=1.8 TeV
PHYSICAL REVIEW D, vol.71, no.3, 2005 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 71 Issue: 3
- Publication Date: 2005
- Doi Number: 10.1103/physrevd.71.031101
- Journal Name: PHYSICAL REVIEW D
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Istanbul University Affiliated: Yes
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.