Scientific article
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Measurement of the helicity fractions of W bosons from top quark decays using fully reconstructed tt events with CDF II

ContributorsCDF Collaboration
Publication date2007

We present a measurement of the fractions F0 and F+ of longitudinally polarized and right-handed W bosons in top-quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318  pb−1. We select tt candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle θ∗, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top-quark rest frame. The cosθ* distribution in the data is determined by full kinematic reconstruction of the tt candidates. We find F0=0.85+0.15−0.22(stat)±0.06(syst) and F+=0.05+0.11−0.05(stat)±0.03(syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F+<0.26 at the 95% confidence level.

Citation (ISO format)
CDF Collaboration. Measurement of the helicity fractions of <em>W</em> bosons from top quark decays using fully reconstructed <em>tt</em> events with CDF II. In: Physical review. D. Particles, fields, gravitation, and cosmology, 2007, vol. 75, n° 05, p. 052001. doi: 10.1103/PhysRevD.75.052001
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Article (Published version)
ISSN of the journal1550-2368

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