Exclusive semileptonic B decays to radially excited charmed mesons are investigated at the first order of heavy quark expansion. The arising leading and subleading Isgur-Wise functions are calculated in the framework of the relativistic quark model. It is found that the ${1/m}_Q$ corrections play an important role and substantially modify the results. An interesting interplay between different corrections is found. As a result the branching ratio for the $\overrightarrow{B}{D}^{\prime }e\nu$ decay is essentially increased by ${1/m}_Q$ corrections, while the one for $\overrightarrow{B}{D}^{*\prime }e\nu$ is only slightly influenced by them.

• Received 16 December 1999

DOI:https://doi.org/10.1103/PhysRevD.62.014032