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 --> ga mma 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 fo und to be in agreement with the result existing in the literature. Usi ng Vector Meson Dominance model, the amplitude for B-s --> phi gamma - -> gamma gamma is calculated as an estimate of the O-7-type contributi ons 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 <( Lambda)over bar>(s), describing bound state effects, and the renormali zation scale mu. (C) 1997 Elsevier Science B.V.