Measurement of the W-boson helicity fractions in top-quark decays at CDF
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 955 pb{sup -1}. We select t{bar t} 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. The cos{theta}* distribution in the data is determined by full kinematic reconstruction of the t{bar t} candidates. We find F{sub 0}= 0.59 {+-} 0.12(stat){sup +0.07}{sub -0.06}(syst) and F{sub +}=-0.03 {+-} 0.06(stat){sup +0.04}{sub -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 +} {le} 0.10 at the 95% confidence level.
- Research Organization:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 908366
- Report Number(s):
- FERMILAB-CONF-07-151-E; arXiv eprint number arXiv:0705.2966
- Country of Publication:
- United States
- Language:
- English
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