Measurement of the inclusive leptonic asymmetry in top-quark pairs that decay to two charged leptons at CDF

We measure the inclusive forward-backward asymmetry of the charged-lepton pseudorapidities from top-quark pairs produced in proton-antiproton collisions and decaying to final states that contain two charged leptons (electrons or muons). The data are collected with the Collider Detector at Fermilab and correspond to an integrated luminosity of 9.1 fb(-1). We measure the leptonic forward-backward asymmetry, A(FB)(ℓ), to be 0.072 ± 0.060 and the leptonic pair forward-backward asymmetry, A(FB)(ℓℓ), to be 0.076 ± 0.082. The measured values can be compared with the standard model predictions of A(FB)(ℓ) = 0.038 ± 0.003 and A(FB)(ℓℓ) = 0.048 ± 0.004, respectively. Additionally, we combine the A(FB)(ℓ) result with a previous determination from a final state with a single lepton and hadronic jets and obtain A(FB)(ℓ) = 0.090(-0.026)(+0.028).

Measurement of B(t→Wb)/B(t→Wq) in top-quark-pair decays using dilepton events and the full CDF Run II data set

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.