WEAK DECAYS IN THE LIGHT-FRONT QUARK-MODEL

We study the form factors of heavy-to-heavy and heavy-to-light weak de cays using the light-front relativistic quark model. For the heavy-to- heavy B --> D() semileptonic decays we calculate the corresponding Is gur-Wise function for the whole kinematic region. For the heavy-to-lig ht B --> P and B --> V semileptonic decays we calculate the form facto rs at q(2) = 0; in particular, we have derived the dependence of the f orm factors on the b-quark mass in the m(b) --> infinity limit. This d ependence cannot be produced by extrapolating the scaling behavior of the form factors at q(max)(2) using the single-pole assumption. This s hows that the q(2) dependence of the form factors in regions far away from the zero recoil could be much more complicated than that predicte d by the single-pole assumption.