We report on the status of the ongoing calculation of multiparticle contributions to the inclusive radiative $\bar{ B} \rightarrow X_s \gamma$ decay at next-to leading order. This effort amounts to the evaluation of the four-particle process $b\rightarrow s \bar{ q} q \gamma$ at the one-loop level, supplemented by the corresponding five-particle tree-level cuts $b\rightarrow s \bar{ q} q \gamma + g$ of the gluon bremsstrahlung. Knowledge of these pieces will formally complete the $\bar{ B} \rightarrow X_s \gamma$ decay at the next-to-leading order. The different steps such as the generation of the amplitude, its renormalization, and the treatment of occurring IR-divergences are discussed. Moreover, we elaborate on the subtleties that arise when treating $\gamma_5$ in $D$ dimensions.
Categories: hep-ph