Measurement of the relative branching fractions of B̅ →D/D*/D**l-ν̅ l 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 BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector. A simultaneous fit to a set of discriminating variables is performed on a sample of B̅ →DXℓ-ν̅ ℓ decays to determine the contributions from the different channels. We measure Γ(B-→Dℓ-ν̅ ℓ)/Γ(B-→DXℓ-ν̅ ℓ)=0.227±0.014±0.016, Γ(B-→D*ℓ-ν̅ ℓ)/Γ(B-→DXℓ-ν̅ ℓ)=0.582±0.018±0.030, and Γ(B-→D**ℓ-ν̅ ℓ)/Γ(B-→DXℓ-ν̅ ℓ)=0.191±0.013±0.019 for the charged B sample, and Γ(B0̅ →Dℓ-ν̅ ℓ)/Γ(B0̅ →DXℓ-ν̅ ℓ)=0.215±0.016±0.013, Γ(B0̅ →D*ℓ-ν̅ ℓ)/Γ(B0̅ →DXℓ-ν̅ ℓ)=0.537±0.031±0.036, and Γ(B0̅ →D**ℓ-ν̅ ℓ)/Γ(B0̅ →DXℓ-ν̅ ℓ)=0.248±0.032±0.030 for the neutral B sample, where uncertainties are statistical and systematic, respectively.