Measurement of Semileptonic B Decays into Orbitally Excited Charmed Mesons

We present a study of B decays into semileptonic final states containing charged and neutral D1(2420) and D2*(2460). The analysis is based on a data sample of 208  fb-1 collected at the Υ(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. With a simultaneous fit to four different decay chains, the semileptonic branching fractions are extracted from measurements of the mass difference Δm=m(D**)-m(D) distributions. Product branching fractions are determined to be B(B+→D10ℓ+νℓ)×B(D10→D*+π-)=(2.97±0.17±0.17)×10-3, B(B+→D2*0ℓ+νℓ)×B(D2*0→D(*)+π-)=(2.29±0.23±0.21)×10-3, B(B0→D1-ℓ+νℓ)×B(D1-→D*0π-)=(2.78±0.24±0.25)×10-3 and B(B0→D2*-ℓ+νℓ)×B(D2*-→D(*)0π-)=(1.77±0.26±0.11)×10-3. In addition we measure the branching ratio Γ(D2*→Dπ-)/Γ(D2*→D(*)π-)=0.62±0.03±0.02.