Determination of the B -> D^*+l-nu Decay Width and |V_{cb}|

TL;DR

This paper measures the CKM matrix element |Vcb| by analyzing B --> D*+ l nu decays, extrapolating the decay rate to the zero-recoil point, and providing a precise experimental determination of |Vcb|F(1).

Contribution

It presents a new experimental determination of |Vcb|F(1) and the branching fraction using a large data sample, improving the precision of these fundamental parameters.

Findings

|Vcb|F(1) = 0.0424 +- 0.0018 (stat) +- 0.0019 (syst)

Branching fraction B(B --> D*+ l nu) = (5.66 +- 0.29 +- 0.33)%

Results are preliminary and based on 3.33 million BBbar events.

Abstract

We determine the CKM matrix element |Vcb| using a sample of 3.33 million BBbar events in the CLEO detector at CESR. We determine the yield of reconstructed B --> D*+ l nu decays as a function of w = v_B . v_D*, and from this we obtain the differential decay rate d\Gamma/dw. By extrapolating the differential decay rate to w=1, the kinematic 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 and is predicted accurately by theory. We find |Vcb| F(1) = 0.0424 +- 0.0018(stat.) +- 0.0019(syst.). We also integrate the differential decay rate over w to obtain B(B --> D*+ l nu) = (5.66 +- 0.29 +- 0.33)%. All results are preliminary.