Two-photon exclusive decays $B_s \to η(η') γγ$ and $B \to K γγ$

Abstract

The exclusive decay modes $B \to K γγ$ and $B_s \to η(η') γγ$ are shown to have significant branching ratios of approximately $0.5\times 10^{-7}$. This first calculation of these modes employs a model based on a cascade transition $B\to Vγ\to Pγγ$ for estimating the long-distance contribution and the process $b\to sγγ$ for the short distance one.