NNLO QCD counterterm contributions to $B$ \to $X_s \gamma$ for the physical value of $m_c$

Understand

One of the most important O($\alpha_s^2$) corrections to the $B \to X_s \gamma$ branching ratio originates from interference of contributions from the current-current and photonic dipole operators.

• Its value has been estimated using an interpolation in the charm quark mass between the known results at $m_c=0$ and for $m_c \ll m_b/2$.
• An explicit calculation for the physical value of $m_c$ is necessary to remove the associated uncertainty.
• In the present work, we evaluate all the ultraviolet counterterm contributions that are relevant for this purpose.