Finite mass corrections for B -> D(*), D** ℓ νdecays in the Bakamjian-Thomas relativistic quark model

الأصل · EN

The Bakamjian-Thomas relativistic quark model for hadron current matrix elements, while non-covariant at finite mass, is successful in the heavy quark limit: form factors are covariant and satisfy Isgur-Wise scaling and Bjorken-Uraltsev sum rules. Motivated by the so-called "1/2 vs. 3/2 puzzle" in B decays to positive parity D**, we examine the implications of the model at finite mass. In the elastic case 1/2- -> 1/2-, the HQET constraints for the O(1/mQ) corrections are analytically fulfilled. A number of satisfying regularities is also found for inelastic transitions. We compute the form factors using the wave functions given by the Godfrey-Isgur potential. For 1/2- → 3/2+ the departures from the heavy quark limit are small, but we find a strong enhancement in 1/2- -> 1/2+ (for 0- -> 0+). This enhancement is linked to a serious difficulty of the model at finite mass for the inelastic transitions, namely a violation of the HQET constraints at zero recoil formulated by Leibovich et al. These are nevertheless satisfied in the non-relativistic limit for the light quark. We conclude that these HQET rigorous constraints are crucial in the construction of a sensible relativistic quark model of inelastic form factors.