Chiral dynamics predictions for eta' -> eta pi pi

TL;DR

This paper analyzes eta' -> eta pi pi decays using large-Nc Chiral Perturbation Theory and Resonance Chiral Theory, incorporating final state interactions and finite-width effects to match experimental data.

Contribution

It provides a comprehensive theoretical study of eta' decays, including unitarization and finite-width effects, improving agreement with experimental Dalitz plot parameters.

Findings

Branching ratios are well understood by the models.

Dalitz plot parameters require pi-pi loop inclusion for accuracy.

Predictions align with recent experimental measurements.

Abstract

The hadronic decays eta' -> eta pi pi are studied in the frameworks of large-Nc Chiral Perturbation Theory, at lowest and next-to-leading orders, and Resonance Chiral Theory in the leading 1/Nc approximation. Higher order effects such as pi-pi final state interactions are taken into account through a detailed unitarization procedure. The inclusion of finite-width effects in the case of RChT is also discussed. The Dalitz plot distribution and the differential branching ratio are computed in both approaches. The predicted Dalitz plot parameters obtained from the different treatments are compared with the most recent measured values. We find that the eta' -> eta pi pi branching ratios are easily understood, while the Dalitz plot parameters require the inclusion of pi-pi loops in order to achieve a reasonable agreement. Our final predictions agree with the experimental measurements. We hope our results to be of relevance for present and future experimental analyses of these decays.