The (Q7, Q1,2) contribution to B¯→Xsγ at Oαs2

A bstract Interference between the photonic dipole operator Q 7 and the current-current operators Q 1,2 gives one of the most important QCD corrections to the ( B ¯ → X s γ decay rate. So far, the O α s 2 ) part of this correction has been known in the heavy charm quark limit only ( m c ≫ m b / 2). Here, we evaluate this part at m c = 0, and use both limits in an updated phenomenological study. Our prediction for the CP- and isospin-averaged branching ratio in the Standard Model reads ℬ s γ S M = 3.36 ± 0.23 × 1 0 − 4 for E γ > 1 . 6 GeV.