Bs-->γγ decay in the two-Higgs-doublet model

The rare B_s-->γγ decay has been investigated in the framework of the two-Higgs-doublet model. It is shown that the branching ratio has a great enhancement in comparison to the standard model (SM) prediction. We have found that the ratio of the square of the CP=1 to CP=-1 amplitudes, \|A⁺\|²/\|A^-\|², which is always less than one in the SM, becomes greater than one for some values of m_H/m_t. We have also calculated the direct CP-violating parameter ɛ'_γγ(-). It is found that for K-->γγ decay its value is greater than the one which follows from the SM, while for B_s-->γγ decay both models have the same predictions. Finally, we compare our results on B_s-->γγ decay with the results of B_s-->μ⁺μ^- and B_s-->μ⁺μ^- decays which are of the same order of the coupling constant.