Factorization in Color-Favored B Meson Decays to Charm

With the improvement of data on $B$ meson decays to various channels it has become possible to test more incisively some factorization predictions made a number of years ago. A concurrent benefit is the ability to constrain the Cabibbo-Kobayashi-Maskawa matrix element $V_{cb}$. Using a simultaneous fit to the rates for the color-favored decays $\ob \to D^{(*)+} \pi^-$ and $\ob \to D^{(*)+} \rho^-$ and to a differential distribution $d \Gamma(\ob \to D^{*+} l^- \bar \nu_l)/ dq^2$ recently measured by the CLEO Collaboration, we find $|V_{cb}| = 0.0460^{+0.0039}_{-0.0036}$, in accord with the fit to the $\ob \to D^{*+} l^- \bar \nu_l$ process alone performed by CLEO. The slope of the universal Isgur-Wise form factor is described by a parameter found to be $\rho^2 = 1.87^{+0.41}_{-0.37}$. Taking the $D_s$ meson decay constant to be $f_{D_s} = 251 \pm 30$ MeV from the world average of direct measurements, we predict satisfactorily the branching ratios for $\ob \to D^{(*)+} D_s^{(*)-}$. Ratios of helicity amplitudes for color-favored processes are also found to be in accord with predictions.