Exclusive and inclusive semileptonic decays of B mesons to D mesons.

We report new measurements of the branching fractions {ital B}({ital B}{sup {minus}}{r arrow}{ital D}{sup 0}{ital l{minus}}{bar {nu}}), {ital B}({ital {bar B}}{sup 0}{r arrow}{ital D}{sup +}{ital l{minus}}{bar {nu}}), and {ital B}({ital B}{sup {minus}}{r arrow}{ital D}{sup *0}{ital l{minus}}{bar {nu}}). Combining these results with our previous measurement of {ital B}({ital {bar B}}{sup 0}{r arrow}{ital D}{sup *+}{ital l{minus}}{bar {nu}}), we find that the ratio of semileptonic widths for final states with a vector meson and pseudoscalar meson is (2.6{sub {minus}0.6{minus}0.8}{sup +1.1+1.0}) and the ratio of charged- to neutral-{ital B}-meson lifetimes is (0.89{plus minus}0.19{plus minus}0.13)({ital f}{sub 00}/{ital f}{sub +{minus}}) where ({ital f}{sub 00}/{ital f}{sub +{minus}}) is the ratio of neutral- to charged-{ital B}-meson production at the {Upsilon}(4{ital S}). From the {ital {bar B}}{r arrow}{ital Dl}{sup {minus}}{bar {nu}} branching fraction, we calculate {vert bar}{ital V}{sub {ital c}{ital b}}{vert bar}=0.040{plus minus}0.006 {plus minus}0.006, where the first error is statistical and the second is systematic and dominated by the uncertainty in the {ital B}-meson lifetime.