Measurement of the W boson helicity in top quark decays

doi:10.2172/919582

Title: Measurement of the W boson helicity in top quark decays

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Abstract

A measurement of the fraction, f ⁺, of right-handed W bosons produced in top quark decays is presented. This analysis is based on a sample corresponding to an integrated luminosity of 370 pb ^-1, collected by the D0 detector at the Fermilab Tevatron p$$\bar{p}$$ Collider at √s = 1.96 TeV. The helicity angle, θ*, is reconstructed for each lepton. f ⁺ is determined by comparing the cos θ* distribution from the data with that for the expected background and signal for various values of f ⁺. The fraction of longitudinal W bosons, f ⁰, is assumed to be 0.7 as predicted by the standard model. This yields f ⁺ = 0.109 ± 0.094 (stat) ± 0.063 (syst), consistent with the standard model prediction of f ⁺ = 3.6x 10 ^-4. The possibility that both f ⁺ and f ⁰ stray from standard model values is also investigated. In this case cos θ* distributions for each possible W helicity state, along with the backgrounds, are fit to the cos θ* distribution for the data. The best fit values are f ⁺ = 0.82 ± 0.30(stat) and f ⁰ = -0.58 ± 0.50(stat).

Authors:

Gmyrek, Bryan David ^[1]

Univ. of Arizona, Tucson, AZ (United States)

Publication Date:: Mon Jan 01 00:00:00 EST 2007

Research Org.:: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 919582

Report Number(s):: FERMILAB-THESIS-2007-32
TRN: US0806446

DOE Contract Number:: AC02-07CH11359

Resource Type:: Thesis/Dissertation

Country of Publication:: United States

Language:: English

Subject:: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; DISTRIBUTION; FERMILAB TEVATRON; HELICITY; INTERMEDIATE BOSONS; LUMINOSITY; STANDARD MODEL; T QUARKS; Experiment-HEP

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                    Gmyrek, Bryan David. Measurement of the W boson helicity in top quark decays.  United States: N. p., 2007. 
        Web.  doi:10.2172/919582.

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                    Gmyrek, Bryan David. Measurement of the W boson helicity in top quark decays.  United States.  doi:10.2172/919582.

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                    Gmyrek, Bryan David. Mon .  
        "Measurement of the W boson helicity in top quark decays".  United States.  
        doi:10.2172/919582.  https://www.osti.gov/servlets/purl/919582.

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@article{osti_919582,

  title        = {Measurement of the W boson helicity in top quark decays},

  author       = {Gmyrek, Bryan David},

  abstractNote = {A measurement of the fraction, f+, of right-handed W bosons produced in top quark decays is presented. This analysis is based on a sample corresponding to an integrated luminosity of 370 pb-1, collected by the D0 detector at the Fermilab Tevatron p$\bar{p}$ Collider at √s = 1.96 TeV. The helicity angle, θ*, is reconstructed for each lepton. f+ is determined by comparing the cos θ* distribution from the data with that for the expected background and signal for various values of f+. The fraction of longitudinal W bosons, f0, is assumed to be 0.7 as predicted by the standard model. This yields f+ = 0.109 ± 0.094 (stat) ± 0.063 (syst), consistent with the standard model prediction of f+ = 3.6x 10-4. The possibility that both f+ and f0 stray from standard model values is also investigated. In this case cos θ* distributions for each possible W helicity state, along with the backgrounds, are fit to the cos θ* distribution for the data. The best fit values are f+ = 0.82 ± 0.30(stat) and f0 = -0.58 ± 0.50(stat).},

  doi          = {10.2172/919582},

  journal      = {},

  number       = ,

  volume       = ,

  place        = {United States},

  year         = {Mon Jan 01 00:00:00 EST 2007},

  month        = {Mon Jan 01 00:00:00 EST 2007}

}

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DOI: 10.2172/919582

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