Leading logarithmic QCD corrections to the Bs → γγ decay rate including long-distance effects through Bs → φγ → γγ

We present leading logarithmic QCD corrections to the decay Bs → γγ in the Standard Model. Further, the form factor F1(0) of Bs → φγ is calculated in the framework of QCD sum rules and found to be in agreement with the result existing in the literature. Using Vector Meson Dominance model, the amplitude for Bs → φγ → γγ is calculated as an estimate of the O7-type contributions to the long-distance effects in the Bs → γγ decay. The resulting branching ratio B(Bs → γγ)SD+LDo7 is analysed in view of its strong dependence on the non-perturbative parameter Λs, describing bound state effects, and the renormalization scale μ.