Measurement of the relative branching fractions of B̄→D/D*/ D**l-ν̄l 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 362×106 BB̄ 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 B̄→DX-ν̄ decays to determine the contributions from the different channels. We measure Γ(B-→D-ν̄)/Γ(B-→DX-ν̄)=0.227±0. 014±0.016, Γ(B-→D*-ν̄)/Γ(B-→DX- ν̄)=0.582±0.018±0.030, and Γ(B-→D **-ν̄)/Γ(B-→DX-ν̄)=0.191±0. 013±0.019 for the charged B sample, and Γ(B0̄→D- ν̄)/Γ(B0̄→DX-ν̄)=0.215±0.016±0. 013, Γ(B0̄→D*-ν̄)/Γ(B0̄→DX- ν̄)=0.537±0.031±0.036, and Γ(B0̄→ D**-ν̄)/Γ(B0̄→DX-ν̄)=0.248±0. 032±0.030 for the neutral B sample, where uncertainties are statistical and systematic, respectively. © 2007 The American Physical Society.