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Title: Measurement of the Helicity of W Bosons in Top-Quark Decays

Authors:
Publication Date:
Research Org.:
COLLABORATION - Fermi
OSTI Identifier:
917531
Report Number(s):
LBNL-61622
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review D; Journal Volume: 73; Related Information: Journal Publication Date: 2006
Country of Publication:
United States
Language:
English

Citation Formats

Abulencia, A. et al. Measurement of the Helicity of W Bosons in Top-Quark Decays. United States: N. p., 2005. Web.
Abulencia, A. et al. Measurement of the Helicity of W Bosons in Top-Quark Decays. United States.
Abulencia, A. et al. Mon . "Measurement of the Helicity of W Bosons in Top-Quark Decays". United States. doi:.
@article{osti_917531,
title = {Measurement of the Helicity of W Bosons in Top-Quark Decays},
author = {Abulencia, A. et al.},
abstractNote = {},
doi = {},
journal = {Physical Review D},
number = ,
volume = 73,
place = {United States},
year = {Mon Nov 07 00:00:00 EST 2005},
month = {Mon Nov 07 00:00:00 EST 2005}
}
  • We measure the branching fraction of the top quark to longitudinally and right-handed polarized W bosons, F{sub 0} and F{sub +}, using approximately 200 pb{sup -1} of p{bar p} collisions collected by the CDF II detector. We analyze two quantities sensitive to the W helicity: the invariant mass of the charged lepton and the bottom-quark jet in the decay t {yields} Wb {yields} {ell}{nu}b (where {ell} = e or {mu}), and the transverse momentum of the charged lepton. We find F{sub 0} = 0.74{sub -0.34}{sup +0.22}, and F{sub +} < 0.27 at the 95% confidence level. These measurements are inmore » agreement with the standard model predictions.« less
  • The authors present a measurement of the fractions F{sub 0} and F{sub +} 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{sup -1}. They select t{bar t} candidate events with one lepton, at least four jets, and missing transverse energy. The helicity measurement uses the decay angle {theta}*, 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 topmore » quark rest frame. The cos {theta}* distribution in the data is determined by full kinematic reconstruction of the t{bar t} candidates. They find F{sub 0} = 0.85{sub -0.22}{sup +0.15}(stat){+-}0.06(syst) and F{sub +} = 0.05{sub -0.05}{sup +0.11}(stat) {+-} 0.03(syst), which is consistent with the standard model prediction. They set an upper limit on the fraction of right-handed W bosons of F{sub +} < 0.26 at the 95% confidence level.« less
  • We use the transverse momentum spectrum of leptons in the decay chain t{yields}bW with W{yields}l{nu} to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a tt sample isolated in 106{+-}4 pb{sup -1} of data collected in pp collisions at {radical}(s)=1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V-A weak decay, we find that the fraction of W 's with zero helicity in the top rest frame is F{sub 0}=0.91{+-}0.37(stat ){+-}0.13(syst) , consistent with the standard model prediction of F{sub 0}=0.70 for a top mass of 175 GeV/c{supmore » 2} . (c) 2000 The American Physical Society.« less
  • We measure the branching fraction of the top quark to longitudinally and right-handed polarized W bosons, F{sub 0} and F{sub +}, using approximately 200 pb{sup -1} of pp collisions collected by the CDF II detector. We analyze two quantities sensitive to the W helicity: the invariant mass of the charged lepton and the bottom-quark jet in the decay t{yields}Wb{yields}l{nu}b (where l=e or {mu}), and the transverse momentum of the charged lepton. Constrained fits yield F{sub 0}=0.74{sub -0.34}{sup +0.22}, and F{sub +}<0.27 at the 95% confidence level. These measurements are consistent with the standard model predictions.
  • We present a measurement of the fractions F{sub 0} and F{sub +} 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{sup -1}. We select tt candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle {theta}*, 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. Themore » cos{theta}* distribution in the data is determined by full kinematic reconstruction of the tt candidates. We find F{sub 0}=0.85{sub -0.22}{sup +0.15}(stat){+-}0.06(syst) and F{sub +}=0.05{sub -0.05}{sup +0.11}(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{sub +}<0.26 at the 95% confidence level.« less