Leading logarithmic QCD corrections to the B-s->gamma gamma decay rate including long-distance effects through B-s->phi gamma->gamma gamma

We present leading logarithmic QCD corrections to the decay B-s --> gamma gamma in the Standard Model. Further, the form factor F-1(0) of B-s --> phi gamma is calculated in the framework of QCD sum rules and found to be in agreement with the result existing in the literature. Using Vector Meson Dominance model, the amplitude for B-s --> phi gamma --> gamma gamma is calculated as an estimate of the O-7-type contributions to the long-distance effects in the B-s --> gamma gamma decay. The resulting branching ratio B(B-s --> gamma gamma)(SD+LDO7) is analysed in view of its strong dependence on the non-perturbative parameter (s), describing bound state effects, and the renormalization scale mu. (C) 1997 Elsevier Science B.V