Leading logarithmic QCD corrections to the Bs→γγ decays in the two-Higgs doublet model

We calculate the leading logarithmic QCD corrections to the decay B-s --> gamma gamma in the two-Higgs doublet model (2HDM) including O-7-type long-distance effects and estimate the restrictions of the 2HDM parameters, tan beta and m(H), using the experimental data of B --> X-s gamma decay provided by the CLEO Collaboration. A lower bound for the charged Higgs mass m(H) as a function of the renormalization scale mu is given for 2HDM model II. We further present the dependencies of the branching ratio Br(B-s --> gamma gamma) and the ratio \A(+)\(2)/\A(-)\(2) on m(H) and tan beta including leading logarithmic QCD corrections. The dependence on the renormalization scale is found to be strong for both ratios. An additional uncertainty arises from the variation of the parameters of the bound state model, (m(b),<(Lambda)over bar>(s)). We see that to look for charged Higgs effects the measurement of the branching ratio Br(B-s --> gamma gamma) is promising. (C) 1998 Elsevier Science B.V.