Improved measurement of vertical bar V-cb vertical bar using (B)over-bar -> D(*)l(nu)over-bar decays

Abstract

We determine the weak coupling \V-cb\ between the b and c quarks using a sample of 3x10(6) B (B) over bar events in the CLEO detector at the Cornell Electron Storage Ring. We determine the yield of reconstructed (B) over bar -->D-*.(ν) over bar decays as a function of w, the boost of the D-* in the B rest frame, and from this we obtain the differential decay rate dGamma/dw. By extrapolating dGamma/dw to w=1, the kinematic end point at which the D-* is at rest relative to the B, we extract the product \V-cb\F(1), where F(1) is the form factor at w=1. Combined with theoretical results for F(1) we determine\V-cb\=0.0469+/-0.0014(stat)+/-0.0020(syst)+/-0.0018(theor).