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Virtual corrections to the decay $b \to s γ$

We calculate the $O(\a_s)$ virtual corrections to the matrix element for $b \to s γ$, taking into account the contributions of the four-Fermi operator $O_2$ and the electromagnetic and color dipole-type operators. The results are combined with existing $O(\a_s)$ Bremsstrahlung corrections in order to obtain the relevant inclusive rate. The new result drastically reduces the large scale dependence of the leading logarithmic approximation. It implies that a very accurate prediction for the branching ratio for $B \to X_s \g $ will become possible once also the corrections to the Wilson coefficients are available.