Study on pure annihilation type B to V gamma decays

We investigate the pure annihilation type radiative $B$ meson decays $B^0 to phi gamma$ and $B_s to rho^0(omega)gamma$ in the soft-collinear effective theory. We consider three types of contributions to the decay amplitudes, including the direct annihilation topology, the contribution from the electro-magnetic penguin operator and the contribution of the neutral vector meson mixings. The numerical analysis shows that the decay amplitudes are dominated by the $omega-phi$ mixing effect in the $B^0 to phigamma$ and $B_s to omegagamma$ modes. The corresponding decay branching ratios are enhanced about three orders of magnitudes relative to the pure annihilation type contribution in these two decay channels. The decay rate of $B_s to rho^0gamma$ is much smaller than that of $B_s to omegagamma$ because of the smaller $rho^0-phi$ mixing. The predicted branching ratios $B(B^{0}rightarrowphigamma)=(3.99^{+1.67}_{-1.46} )times10^{-9},,B(B_srightarrowomegagamma)=(2.01^{+0.81}_{-0.71} )times10^{-7}$ are to be tested by the Belle-II and LHC-b experiments.