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Title: Measurement of the W-boson helicity fractions in top-quark decays at CDF

Abstract

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.

Authors:
;
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
908366
Report Number(s):
FERMILAB-CONF-07-151-E
arXiv eprint number arXiv:0705.2966; TRN: US0703674
DOE Contract Number:  
AC02-07CH11359
Resource Type:
Conference
Resource Relation:
Conference: To appear in the proceedings of 42nd Rencontres de Moriond on QCD and Hadronic Interactions, La Thuile, Italy, 17-24 Mar 2007
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; DECAY; DISTRIBUTION; FERMILAB COLLIDER DETECTOR; FORECASTING; HELICITY; INTERMEDIATE BOSONS; LUMINOSITY; QUANTUM CHROMODYNAMICS; STANDARD MODEL; TRANSVERSE ENERGY; T QUARKS; Experiment-HEP

Citation Formats

Chwalek, Thorsten, and /Karlsruhe U., EKP. Measurement of the W-boson helicity fractions in top-quark decays at CDF. United States: N. p., 2007. Web.
Chwalek, Thorsten, & /Karlsruhe U., EKP. Measurement of the W-boson helicity fractions in top-quark decays at CDF. United States.
Chwalek, Thorsten, and /Karlsruhe U., EKP. Tue . "Measurement of the W-boson helicity fractions in top-quark decays at CDF". United States. doi:. https://www.osti.gov/servlets/purl/908366.
@article{osti_908366,
title = {Measurement of the W-boson helicity fractions in top-quark decays at CDF},
author = {Chwalek, Thorsten and /Karlsruhe U., EKP},
abstractNote = {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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}

Conference:
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