We present a measurement of the ratio of top-quark branching
fractions R = B(t →Wb)/B(t →Wq), where q represents quarks
of type b, s, or d, in the final state with a lepton and hadronic jets.
The measurement uses sqrt(s) = 1.96 TeV proton-antiproton collision data
from 8.7fb-1 of integrated luminosity collected with the Collider Detector
at Fermilab during Run II of the Tevatron. We simultaneously measure R
= 0.94 +- 0.09 (stat+syst) and the t anti-t production cross section
sigma_tt = 7.5 +-1.0 (stat+syst) pb. The Cabibbo-Kobayashi-Maskawa
matrix element |Vtb| = 0.97+-0.05 (stat+syst) is extracted assuming
three generations of quarks, and a lower limit of |Vtb| > 0.89 at 95%
credibility level is set.
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Updated: Tuesday, 2013 June 18 16:21:52 CDT automatically from input from Barbara Hehner