Exclusive and inclusive semileptonic decays ofBmesons toDmesons

We report new measurements of the branching fractions $B(B^{-}\to D^0{l}^{-}\overline{\nu })$, $B({\overline{B}}^0\to D^{+}{l}^{-}\overline{\nu })$, and $B(B^{-}\to D^{*0\mathrm{}}{l}^{-}\overline{\nu })$. Combining these results with our previous measurement of $B({\overline{B}}^0\to D^{*+}{l}^{-}\overline{\nu })$, we find that the ratio of semileptonic widths for final states with a vector meson and pseudoscalar meson is (${2.6}_{-0.6-0.8\mathrm{}}^{+1.1+1.0\mathrm{}}$) and the ratio of charged- to neutral-$B$-meson lifetimes is $(0.89\mathrm{}\pm 0.19\pm 0.13)\left(\frac{f_{00}}{f_{+-}}\right)$ where ($\frac{f_{00}}{f_{+-}}$) is the ratio of neutral- to charged-$B$-meson production at the $\Upsilon \mathrm{}\left(4S\right)\mathrm{}$. From the $\overline{B}\to D{l}^{-}\overline{\nu }$ branching fraction, we calculate $\left|V_{\mathrm{cb}}\right|=0.040\mathrm{}\pm 0.006\pm 0.006$, where the first error is statistical and the second is systematic and dominated by the uncertainty in the $B$-meson lifetime.