CERN-TH/99-175 Heavy quark 1/mQ contributions in semileptonic B decays to

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/mQ 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 the heavy quark expansion and result in a suppression of B → D 0eν and B → D 1eν 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/mQ corrections to be very important, and their account results in a substantial enhancement of B → D1eν and B → D 0eν decay rates. CERN-TH/99-175 June 1999 On leave of absence from the Russian Academy of Sciences, Scientific Council for Cybernetics, Vavilov Street 40, Moscow 117333, Russia.