Measurement of the relative branching fractions of ¯¯¯B→D/D∗/D**l−¯νl decays in events with a fully reconstructed B meson

We determine the relative branching fractions of semileptonic B decays to charmed final states. The measurement is performed on the recoil from a fully reconstructed B meson in a sample of 362 × 10 6 B ¯¯¯ B pairs collected at the Υ ( 4 S ) resonance with the BABAR detector. A simultaneous fit to a set of discriminating variables is performed on a sample of ¯¯¯ B → D X ℓ − ¯ ν ℓ decays to determine the contributions from the different channels. We measure Γ ( B − → D ℓ − ¯ ν ℓ ) / Γ ( B − → D X ℓ − ¯ ν ℓ ) = 0.227 ± 0.014 ± 0.016 , Γ ( B − → D ∗ ℓ − ¯ ν ℓ ) / Γ ( B − → D X ℓ − ¯ ν ℓ ) = 0.582 ± 0.018 ± 0.030 , and Γ ( B − → D ** ℓ − ¯ ν ℓ ) / Γ ( B − → D X ℓ − ¯ ν ℓ ) = 0.191 ± 0.013 ± 0.019 for the charged B sample, and Γ ( ¯¯¯¯¯ B 0 → D ℓ − ¯ ν ℓ ) / Γ ( ¯¯¯¯¯ B 0 → D X ℓ − ¯ ν ℓ ) = 0.215 ± 0.016 ± 0.013 , Γ ( ¯¯¯¯¯ B 0 → D ∗ ℓ − ¯ ν ℓ ) / Γ ( ¯¯¯¯¯ B 0 → D X ℓ − ¯ ν ℓ ) = 0.537 ± 0.031 ± 0.036 , and Γ ( ¯¯¯¯¯ B 0 → D ** ℓ − ¯ ν ℓ ) / Γ ( ¯¯¯¯¯ B 0 → D X ℓ − ¯ ν ℓ ) = 0.248 ± 0.032 ± 0.030 for the neutral B sample, where uncertainties are statistical and systematic, respectively