SEMILEPTONIC DECAYS OF B-C MESONS IN LIGHT-FRONT DYNAMICS AND CORRECTIONS TO THE EFFECTIVE THEORY OF HEAVY QUARKS

Light-front dynamics is used to study the decays B --> Dl nu(l) and B --> Dl nu(l). A necessary criterion of self-consistency in determinin g form factors on the basis of the matrix elements of the ''good'' and transverse components of the vector and axial-vector currents is form ulated. It is shown that the well-known procedure employing only the g ood component J(+) of the current is not always correct, because form factors determined according to this scheme can generally involve nonp hysical contributions. The relativistic potential model is used to cal culate form factors numerically. The results of these calculations are compared with available experimental data and with the results presen ted by other authors. It is demonstrated that, for the transition B -- > Dl nu(l), corrections to the effective theory of heavy quarks can a mount to 5-10%. It is also shown that the partial width with respect t o the decay B --> Dl nu(l) is in accord with experimental data, provi ded that the D meson involves a 0.5% admixture of the D wave.