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The Double Radiative Decays Bγγ in the Heavy Quark Limit

Stefan W. Bosch, Gerhard Buchalla

hep-pharXiv:hep-ph/0208202

Abstract

We analyze the double radiative B-meson decays Bs -> gamma gamma and Bd -> gamma gamma in QCD factorization based on the heavy-quark limit mb >> LambdaQCD. We systematically discuss the various contributions to these exclusive processes. The dominant effect arises from the magnetic-moment type transition b -> s(d) gamma where an additional photon is emitted from the light quark (one-particle reducible diagram). The contributions from one-particle irreducible diagrams are power suppressed. We argue that they are still calculable within QCD factorization. They are used to compute the CP-asymmetries in B -> gamma gamma and to estimate so-called long-distance contributions in B and D -> gamma gamma. Numerical results are presented for branching ratios and CP asymmetries.

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