Leading logarithmic QCD corrections to the B_s --> γγdecay rate including long-distance effects through B_s --> ϕγ--> γγ

Abstract

We present leading logarithmic QCD corrections to the decay B_s --> γγin the Standard Model. Further, the form factor F_{1}(0) of B_s --> ϕγis 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 B_s --> ϕγ-->γγis calculated as an estimate of the O_7-type contributions to the long-distance effects in the B_s --> γγdecay. The resulting branching ratio B(B_s --> γγ)_{SD+LD_{O_7}} is analysed in view of its strong dependence on the non-perturbative parameter $\barΛ_s$, describing bound state effects, and the renormalization scale $μ$. .