Heavy quark1/mQcontributions in semileptonicBdecays to orbitally excitedDmesons

Exclusive semileptonic decays of B mesons to orbitally excited D mesons are considered beyond the infinitely heavy quark limit in the framework of the relativistic quark model based on the quasipotential approach. This model agrees with the structure of heavy quark mass corrections predicted by the heavy quark effective theory and allows the determination of corresponding leading and subleading Isgur-Wise functions. It is found that both relativistic and ${1/m}_Q$ contributions significantly influence the decay rates. Thus, relativistic transformations of the meson wave functions (Wigner rotation of the light quark spin) already contribute at leading order of heavy quark expansion and result in a suppression of $\overrightarrow{B}{D}_0^{*}e\nu$ and $\overrightarrow{B}{D}_1^{*}e\nu$ decay rates. On the other hand, the vanishing of the decay matrix elements at zero recoil of a final $D^{**}$ meson in the infinitely heavy quark mass limit makes the ${1/m}_Q$ corrections very important, and their account results in a substantial enhancement of $\overrightarrow{B}{D}_{1}e\nu$ and $\overrightarrow{B}{D}_0^{*}e\nu$ decay rates.