QCD corrections to b→sγγ and exclusive Bs→γγ decay

The short distance QCD corrections to b→sγγ are calculated in the leading logarithmic approximation. The equivalence of operator basis reduction for S-matrix elements by using the equations of motion or by proving a low energy theorem is discussed. We apply the above results to the exclusive Bs→γγ decay. The branching ratio of this decay is found to be 5×10−7 in the Standard Model. We also found that QCD corrections modify considerably the ratio between CP-even and CP-odd two-photon amplitudes.