Leading logarithmic QCD corrections to the B_s --> γγdecays in the two Higgs doublet model

Abstract

We calculate the leading logarithmic QCD corrections to the decay B_s --> γγin the two Higgs doublet model (2HDM) including O_7 type long distance effects and estimate the restrictions of the 2HDM parameters, tanβand m_H, using the experimental data of B --> X_s γdecay provided by the CLEO collaboration. A lower bound for the charged Higgs mass m_H as a function of the renormalization scale μis given for 2HDM model II. We further present the dependencies of the branching ratio Br(B_s --> γγ) and the ratio |A^{+}|^2/|A^{-}|^2 on m_H and tanβincluding 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, \barΛ_s). We see, that to look for charged Higgs effects the measurement of the branching ratio Br(B_s --> γγ) is promising.