Measurement of R=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 protonantiproton collision data at center-of-mass energy 1.96 TeV, corresponding to an integrated luminosity of 8.7 fb(sub -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(sup tb) = 0.93 plus or minus 0.04, assuming three generations of quarks. Under these assumptions, a lower limit of V(sup tb) greater than 0.85(0.87) at 95 (90) % credibility level is set.