LEADING LOGARITHMIC QCD CORRECTIONS TO THE B-S-]GAMMA-GAMMA DECAYS INTHE 2-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-ty pe long-distance effects and estimate the restrictions of the 2HDM par ameters, tan beta and m(H), using the experimental data of B --> X-s g amma decay provided by the CLEO Collaboration. A lower bound for the c harged Higgs mass m(H) as a function of the renormalization scale mu i s 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 fo r 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 Elsevie r Science B.V.