The Q_{1,2}-Q_7 interference contributions to b -> s gamma at O(alpha_s^2) for the physical value of m_c

TL;DR

This paper calculates second-order QCD corrections to the b -> s gamma decay process, focusing on interference effects between specific operators, to improve theoretical predictions matching upcoming experimental precision.

Contribution

It provides a novel 4-loop level calculation of interference contributions between Q_1, Q_2, and Q_7 operators in b -> s gamma decay, aligning with recent parallel results.

Findings

Results agree with Fael et al.'s 3-loop amplitude approach.

Partial results match those of Greub et al.

Enhances theoretical precision for B -> X_s gamma decay predictions.

Abstract

The B -> X_s gamma branching ratio is currently measured with around 5% accuracy. Further improvement is expected from Belle II. To match such a precision on the theoretical side, evaluation of O(alpha_s^2) corrections to the partonic decay b -> X_s^part gamma are necessary, which includes the b -> s gamma, b -> s g gamma, b -> s g g gamma, b -> s qbar q gamma decay channels. Here, we evaluate the unrenormalized contribution to b -> s gamma that stems from the interference of the photonic dipole operator Q_7 and the current-current operators Q_1 and Q_2. Our results, obtained in the cut propagator approach at the 4-loop level, agree with those found in parallel by Fael et al. who have applied the amplitude approach at the 3-loop level. Partial results for the same quantities recently determined by Greub et al. agree with our findings, too.