Towards a next-to-leading logarithmic result in $B \to X_s \gamma$

Abstract

The calculation of the $O(\a_s)$ virtual corrections to the matrix element of the inclusive decay $b \to s \gamma$ is reported. These contributions drastically reduce the large renormalization scale dependence of the leading logarithmic calculation. Combining these results with the preliminary result for the Wilson coefficient $C_7(m_b)$ calculated recently by Chetyrkin, Misiak, and M\"unz, we estimate the branching ratio to be $BR(B \to X_s \gamma)=(3.25 \pm 0.50) \times 10^{-4}$.