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Completing the NLO QCD calculation of B -> Xs gamma

Andrzej J. Buras·Andrzej Czarnecki·Mikolaj Misiak·Joerg Urban
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Abstract

We evaluate two-loop b -> s gamma matrix elements of all the four-quark operators containing no derivatives. Contrary to previous calculations, no expansion in the mass ratio mc/mb is performed, and all the possible Dirac and flavor structures are included. Consequently, we are able to provide the last item in the NLO analysis of B -> Xs gamma that has been missing so far, namely the two-loop matrix elements of the QCD-penguin operators. Due to smallness of the Wilson coefficients of those operators in the Standard Model, their effect on the branching ratio is small: a reduction by roughly 1%. We find BR[ B -> Xs gamma]_{E_gamma > 1.6 GeV} = (3.57 +_ 0.30)*10^{-4}.

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Andrzej J. Buras, Andrzej Czarnecki, Mikolaj Misiak, Joerg Urban. 2002-03-14. Completing the NLO QCD calculation of B -> Xs gamma. https://doi.org/10.1016/s0550-3213(02)00261-4

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