Towards B -> X_s gamma at the NNLO in QCD without interpolation in m_c

Understand

Strengthening constraints on new physics from the B -> X_s gamma branching ratio requires improving accuracy in the measurements and the Standard Model predictions.

• To match the expected Belle-II accuracy, Next-to-Next-to-Leading Order (NNLO) QCD corrections must be calculated without the so-far employed interpolation in the charm-quark mass m_c.
• In the process of evaluating such corrections at the physical value of m_c, we have finalized the part coming from diagrams with closed fermion loops on the gluon lines that contribute to the interference of the current-current and photonic dipole operators.
• We confirm several published results for corrections of this type, and supplement them with a previously uncalculated piece.