Low energy effective Lagrangian description of η and η′ decays

Abstract

A chiral Lagrangian incorporating a resolution of theU(1) problem is used to study some aspects of the η−η′ system. Mass relations, mixing angle predictions, and the 3π decay modes of η and η−η′ are obtained to be of the correct order of magnitude. Supplementing this Lagrangian with certain four derivative terms gives a rate for η−η′→ηππ which is nonvanishing in the chiral limit and in reasonable agreement with experiment. Some of the radiative decays of η and η′ are also discussed.