Measurement of B(t →Wb)/B(t → Wq) in Top-Quark-Pair Decays Using Dilepton Events and the Full CDF Run Ⅱ Data Set

摘要

We present a measurement of the ratio of the top-quark branching fractions R = B(t → Wb)/B(t →Wq), where q represents any quark flavor, in events with two charged leptons, imbalance in total transverse energy, and at least two jets. The measurement uses proton-antiproton collision data at center-of-mass energy 1.96 TeV, corresponding to an integrated luminosity of 8.7 fb~(-1) collected with the Collider Detector at Fermilab during Run Ⅱ of the Tevatron. We measure R to be 0.87 ± 0.07, and extract the magnitude of the top-bottom quark coupling to be |V_(tb)| = 0.93 ±0.04, assuming three generations of quarks. Under these assumptions, a lower limit of |V_(tb)| ＞ 0.85(0.87) at 95% (90%) credibility level is set.