$\eta \to \pi^0 \gamma \gamma$ decay within a chiral unitary approach revisited

TL;DR

This paper reevaluates the decay width of the eta meson decaying into a neutral pion and two photons using updated experimental data and a chiral unitary approach, achieving improved accuracy and better agreement with recent experiments.

Contribution

It provides a revised theoretical calculation of the $ ext{eta} o ext{pi}^0 ext{gamma} ext{gamma}$ decay width incorporating new PDG data and compares well with recent experimental results.

Findings

Decay width uncertainty reduced by nearly 50%.

Theoretical results agree well with AGS and MAMI data.

Invariant mass distributions match experimental observations.

Abstract

In view of the recent experimental developments on the experimental side in the $\eta \to \pi^0 \gamma \gamma$ decay, and the fact that the Particle Data Group in the on line edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of \cite{eta}, a reevaluation of the decay width of the $\eta$ in this channel has been done, reducing its uncertainty by almost a factor of two. The new input of the PDG is used and invariant mass distributions and total widths are compared with the most recent results from AGS, MAMI and preliminary ones of KLOE. The agreement of the theory with the AGS and MAMI data is very good, both for the total rates as well as for the invariant mass distributions of the two photons.