Flavor-changing two-photon decay.

Abstract

We discuss a class of flavor-changing two-photon rare decays, such as b\ensuremath{\rightarrow}s\ensuremath{\gamma}\ensuremath{\gamma}. Both dimension-six and dimension-eight operators are shown to contribute to these decays. For a heavy top, contributions from dimension-six operators become sizable and even dominant. They can be simply related to a single-photon decay like b\ensuremath{\rightarrow}s\ensuremath{\gamma}. Implications for ${\mathit{B}}_{\mathit{s}}$\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma} are discussed, especially with regard to the spin orientations of the photons.