Form Factor $A_0(q^2)$, Non Leptonic $D(B)\to PV$ Transitions and Rare $B\to K^{\ast }\gamma$ Decays

Abstract

We use three-point function QCD sum rules to calculate the form factor $A_0(q^2)$ appearing in the matrix element of the flavour-changing axial current between the $D(B)$ state and a vector meson state. We describe the role of this form factor in nonleptonic $D(B)\to PV$ decays and analyze the light $SU(3{)}_F$ symmetry breaking effects. We also discuss a proposal to relate the branching ratio of $B\to K^{\ast }\gamma$ to the spectrum of the semileptonic $B\to \rho \ell \nu$ decay.

Comments: LaTex, 17 pages, 3 figures (PostScript files appended at the end), BARI-TH/94-174, DSF-T-94/12, INFN-NA-IV-94/12