THE SEMILEPTONIC EXCLUSIVE B-DECAY AND D-DECAY ON THE LIGHT-FRONT

We present a comprehensive account of a relativistic quark model on th e light front which gives the form factors of weak hadronic currents a mong heavy pseudoscalar and vector mesons in the complete kinematic re gion 0 less than or equal to q(2) less than or equal to q(max)(2). For the numerical investigations of the B --> Dl nu(l), B --> rho l nu(l ), D --> Klv(l) and D --> rho l nu(l) semileptonic decays equal time wave functions using the updated Values of the ISGW model are adopted. From the available experimental information on branching fractions BR (B --> Dl nu(l)) and BR(B --> rho l gamma(l)) the CKM parameters \V-c b\ and \V-ab\ are estimated to be \V-cb\ = 0.036 +/- 0.002, \V-ab\ = 0 .0033 +/- 0.0005. It is shown that the q(2) distribution for the decay B --> Dl nu(l) will allow for an accurate test of the value of \V-cb \. The model is compared to the experimental data, QCD sum rules and l attice calculations. (C) 1997 Elsevier Science B.V.