Measurement of B(t→Wb)/B(t→Wq) at s=1.96TeV

The authors present the measurement of R = {Beta}(t {yields} Wb)/{Beta}(t {yields} Wq) in p{bar p} collisions at {radical}s = 1.96 TeV, using 230 pb{sup -1} of data collected by the D0 experiment at the Fermilab Tevatron Collider. They fit simultaneously R and the number (N{sub t{bar t}}) of selected top quark pairs (t{bar t}), to the number of identified b-quark jets in events with one electron or one muon, three or more jets, and high transverse energy imbalance. To improve sensitivity, kinematical properties of events with no identified b-quark jets are included in the fit. They measure R = 1.03{sub -0.17}{sup +0.19}(stat+syst), in good agreement with the standard model. They set lower limits of R > 0.61 and |V{sub tb}| > 0.78 at 95% confidence level.