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arXiv · 1209.0965

Tree-level contributions to B -> Xs gamma

Maciej Kaminski·Mikolaj Misiak·Michal Poradzinski
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Abstract

Weak radiative decay B -> X_s gamma is known to be a loop-generated process. However, it does receive tree-level contributions from CKM-suppressed b -> u ubar s gamma transitions. In the present paper, we evaluate such contributions together with similar ones from the QCD penguin operators. For a low value of the photon energy cutoff E_0 ~ m_b/20 that has often been used in the literature, they can enhance the inclusive branching ratio by more than 10%. For E_0 = 1.6 GeV or higher, the effect does not exceed 0.4%, which is due to phase-space suppression. Our perturbative results contain collinear logarithms that depend on the light quark masses m_q (q=u,d,s). We have allowed m_b/m_q to vary from 10 to 50, which corresponds to values of m_q that are typical for the constituent quark masses. Such a rough method of estimation may be improved in the future with the help of fragmentation functions once the considered effects begin to matter in the overall error budget for BR(B -> X_s gamma).

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Maciej Kaminski, Mikolaj Misiak, Michal Poradzinski. 2014-12-01. Tree-level contributions to B -> Xs gamma. https://doi.org/10.1103/physrevd.86.094004

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