Improved Measurement of |Vcb| using B --> D* l nu Decays

Abstract

We determine the weak coupling |Vcb| between the b and c quarks using a sample of 3 million BB-bar events in the CLEO detector at the Cornell Electron Storage Ring. We determine the yield of reconstructed B --> D* l nu 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 |Vcb|F(1), where F(1) is the form factor at w=1. We find |Vcb|F(1) = 0.0431 +- 0.0013 (stat.) +- 0.0018 (syst.).