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Electroweak effects in radiative B decays

Paolo Gambino·Ulrich Haisch
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Abstract

We compute the two-loop electroweak corrections to the radiative decays of the B meson in the SM. Electroweak effects reduce the Wilson coefficient C_7^eff(mw) by 2.6% for a light Higgs boson of about 100 GeV and are less important for a heavier Higgs. The leading term of a heavy top expansion of our result differs from the one obtained in the gaugeless approximation where only top quark Yukawa couplings are considered: we discuss the origin of the discrepancy and provide a criterion for the validity of the gaugeless approximation. As a byproduct of the calculation we also obtain the O(alpha) corrections to the Wilson coefficient of the four-fermion operator Q_2. A careful analysis of the interplay between electroweak and QCD effects leads to an overall 2% reduction of the total branching ratio for B -> X_s gamma due to purely electroweak corrections. For a light Higgs boson, the up-to-date SM prediction is BR_gamma=3.29 10^-4.

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Paolo Gambino, Ulrich Haisch. 2000-07-24. Electroweak effects in radiative B decays. https://doi.org/10.1088/1126-6708%2F2000%2F09%2F001

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