Eta and Eta' physics

TL;DR

This paper discusses the significance of eta and eta' decays in theoretical and experimental physics, focusing on recent two-loop ChPT calculations of eta to three pions and their implications for understanding anomalies.

Contribution

It presents new two-loop order calculations of eta to three pions in ChPT and compares them with dispersive approaches, highlighting unresolved issues.

Findings

Two-loop ChPT results differ from dispersive calculations

Eta and eta' decays are useful for studying quantum anomalies

Recent calculations challenge previous theoretical assumptions

Abstract

This talk describes the reasons why $\eta$ and $\eta^\prime$ decays are an interesting topic of study for both theory and experiment. The main part discusses the results of the recent calculation of $\eta\to3\pi$ at two-loop order in ChPT. Some puzzling aspects of the results compared to earlier dispersive calculations are highlighted. I also like to remind the reader of the use of $\eta$ and $\eta^\prime$ decays for studying the anomaly.