Heavy-to-light form factors in the final hadron large energy limit: Covariant quark model approach

We prove the full covariance of the heavy-to-light weak current matrix elem ents based on the Bakamjian-Thomas construction of relativistic quark model s, in the heavy mass limit for the parent hadron and the large energy limit for the daughter one. Moreover, this quark model representation of the hea vy-to-light form factors fulfills the general relations that were recently argued to hold in the corresponding limit of QCD, namely that there are onl y three independent form factors describing the B --> pi(rho) matrix elemen ts, as well as the factorized scaling law similar to root M z(E) of the for m factors with respect to the heavy mass M and large energy E. These result s constitute another good property of the quark models a la Bakamjian-Thoma s, which were previously shown to exhibit covariance and Isgur-Wise scaling in the heavy-to-heavy case. (C) 1999 Elsevier Science B.V. All rights rese rved.