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

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

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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:: Chwalek, Thorsten; /Karlsruhe U., EKP

Publication Date:: Tue May 01 00:00:00 EDT 2007

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

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                    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.

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                    Chwalek, Thorsten, & /Karlsruhe U., EKP. Measurement of the W-boson helicity fractions in top-quark decays at CDF.  United States.

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                    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.

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@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}

}

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