Semileptonic $B$ and $B_{s}$ decays into orbitally excited charmed   mesons
  The BaBar Collaboration has recently reported products of branching fractions that include $B$ meson semileptonic decays into final states with charged and neutral $D_{1}(2420)$ and $D_{2}^{\ast}(2460)$, two narrow orbitally excited charmed mesons. We evaluate these branching fractions, together with those concerning $D_{0}^{\ast}(2400)$ and $D_{1}'(2430)$ mesons, within the framework of a constituent quark model. The calculation is performed in two steps, one of which involves a semileptonic decay and the other is mediated by a strong process. Our results are in agreement with the experimental data. We also extend the study to semileptonic decays of $B_{s}$ into orbitally excited charmed-strange mesons, providing predictions to the possible measurements to be carried out at LHC. 
J. Segovia, C. Albertus, D. R. Entem, F. Fern\'andez, E. Hern\'andez   and M. A. P\'erez-Garc\'ia
hep-ph hep-ex