Speaker
Description
Theoretical predictions in hadron physics are often limited by non-perturbative uncertainties in QCD. Nevertheless, several phenomenologically important processes require improved theoretical control. Effective field theories, such as Soft-Collinear Effective Theory (SCET) and Heavy Quark Effective Theory (HQET), provide powerful tools to overcome these limitations by exploiting factorisation.
A particularly interesting class of observables arises in flavour physics, and in particular in inclusive $B\to X_s\gamma$ decays. Among the resolved contributions to this process, the dominant theoretical uncertainty currently originates from the interference between the WET operators $Q_1^q$ and $Q_{7\gamma}$, which corresponds to a non-local subleading power corrections.
In this work, we derive a factorisation formula for this interference that is suitable for the inclusion of perturbative corrections. The factorised expression involves four distinct functions. We present explicit results for all of them, with particular emphasis on the renormalisation-group evolution of the shape function $g_{17}$, a generalised light-cone distribution amplitude depending on both light-cone directions, and the two-loop penguin jet function, which was computed fully analytically.
These ingredients complete the NLO corrections to the $Q_1^q-Q_{7\gamma}$ interference. Moreover, they provide important insight into the technical structure of these higher-order corrections. These results are expected to be highly relevant for future precision studies at subleading power.