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 D(1)(2420) and D(2)*(2460). The analysis is based on a data sample of 208 fb(-1) collected at the Y(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 Delta m = m(D**) - m(D) distribution. Product branching fractions are determined to be B(B(+) -> D(1)(0)l(+)nu(l)) x B(D(1)(0) -> D(*+)pi(-)) = (2.97 +/- 0.17 +/- 0.17) x 10(-3), B(B(+) -> D(2)*l(+)nu(e)) x B(D(2)*(0) -> D((*)+)pi(-)) = (2.29 +/- 0.23 +/- 0.21) x 10(-3), B(B(0) -> D(1)(-)l(+)nu(l)) x B(D(1)(-) -> D*(0)pi(-)) = (2.78 +/- 0.24 +/- 0.25) x 10(-3) and B(B(0) -> D(2)*(-)l(+)nu(l)) x B(D(2)(*-) -> D((*)0)pi(-)) = (1.77 +/- 0.26 +/- 0.11) x 10(-3). In addition we measure the branching ratio Gamma(D2* -> D pi(-))/Gamma(D(2)* -> D((*))pi(-)) = 0.62 +/- 0.03 +/- 0.02.