Annihilation type rare radiative $B_{(s)}\to V\gamma$ decays

Abstract

We obtain predictions for a number of radiative decays $B_{(s)}\to V\gamma$, $V$ the vector meson, which proceed through the weak-annihilation mechanism. Within the factorization approximation, we take into account the photon emission from the $B$-meson loop and from the vector-meson loop; the latter subprocesses were not considered in the previous analyses but are found to have sizeable impact on the $B_{(s)}\to V\gamma$ decay rate. The highest branching ratios for the weak-annihilation reactions reported here are ${\cal B}(\bar B^0_s\to J/\psi\gamma)=1.5\cdot 10^{-7}$ and ${\cal B}(B^-\to \bar D_s^{*-}\gamma)=1.7\cdot 10^{-7}$, the estimated accuracy of these predictions being at the level of 20\%.