Measurement of W Boson Polarization in Top Quark Decay
- Univ. of Illinois, Urbana-Champaign, IL (United States)
A measurement of the polarization of the W boson from top quark decay is an excellent test of the V-A form of the charged-current weak interaction in the standard model. Since the longitudinal W boson is intimately related to the electroweak symmetry breaking mechanism, and the standard model gives a specific prediction for the fraction of longitudinal W bosons from top decays, it is of particular interest for study. This thesis presents a measurement of W boson polarization in top quark decays through an analysis of the cosθ* distribution in the lepton-plus-jets channel of t$$\bar{t}$$ candidate events from p$$\bar{p}$$ collisions at √s = 1.96 TeV. This measurement uses an integrated luminosity of ~ 162 pb-1 of data collected with the CDF Run II detector, resulting in 31 t$$\bar{t}$$ candidate events with at least one identified b jet. Using a binned likelihood fit to the cosθ* distribution from the t$$\bar{t}$$ candidate events found in this sample, the fraction of W bosons with longitudinal polarization is determined to be F0 = 0.99$$+0.29\atop{-0.35}$$stat.) ± 0.19(syst.), F0 > 0.33 @ 95% CL. This result is consistent with the standard model prediction, given a top quark mass of 174.3 GeV/c2, of F0 = 0.701 ± 0.012.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76CH03000
- OSTI ID:
- 15017261
- Report Number(s):
- FERMILAB-THESIS-2004-49; TRN: US0605148
- Country of Publication:
- United States
- Language:
- English
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