Paper detail

Measurement of B(t->Wb)/B(t->Wq) at sqrt(s) = 1.96 TeV

We present the measurement of R = B(t->Wb)/B(t->Wq) in ppbar collisions at sqrt(s) = 1.96 TeV, using 230 pb-1 of data collected by the DO experiment at the Fermilab Tevatron Collider. We fit simultaneously R and the number of selected top quark pairs (ttbar), 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. We measure R = 1.03 +0.19 -0.17 (stat+syst), in good agreement with the standard model. We set lower limits of R > 0.61 and |V_tb| > 0.78 at 95% confidence level.