Exclusive semi-leptonic decays of bottom mesons in the spectator quark model

Abstract

We calculate the exclusive semileptonic bottom meson decays\(B \to D(D*) + l^ - + \bar v_l \) in the spectator quark model. The helicity structure of the mesonic current transitionsB→D(D*) is matched to the helicity structure of the free quark current transitionsb→c at minimum momentum transferq2=0. The results are continued toq2≠=0 by pole-dominated form factors. Our results are compared to recent calculations that use quark model dynamics at maximum momentum transferq max 2 = (M1 −M2)2. We find agreement atq max 2 . Atq2=0 there are significant differences between the predictions of the two approaches leading to marked differences in the predictions for the shape of the lepton energy spectrum, the shape of theq2-distribution, and the helicity composition of the transition measurable in the angular distributions of the decaysD*→Dπ and\(W_{virtual}^ - \to l^ - + \bar v_l \).