$K_{S}$ $\to$ $\gamma \gamma$ at one-loop revisited

TL;DR

This paper recalculates the decay amplitude for $K_{S} o \gamma \gamma$ at one-loop order in chiral perturbation theory, including the weak mass term, resulting in predictions that align well with experimental data.

Contribution

It introduces the inclusion of the weak mass term $G_{8}^{\prime}$ in the calculation, improving the theoretical prediction for the decay rate.

Findings

The decay rate prediction now agrees with experimental measurements.

Including the weak mass term significantly impacts the theoretical results.

The approach refines previous calculations by considering previously neglected contributions.

Abstract

We have calculated the decay amplitude for the process $K_{S}$ $\to$ $\gamma \gamma$ at one loop order in chiral perturbation theory. As a new improvement we have included the weak mass term which is only relevant for processes with external fields in the final state. This term was ignored in earlier publications for this decay. We find that the inclusion of $G_{8}^{\prime}$ brings the theoretical decay rate into a good agreement with experiment.