Low energy effective lagrangian description of η and η' decays

A chiral Lagrangian incorporating a resolution of the U(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' are obtained to be of the correct order of magnitude. Supplementing this Lagrangian with certain four derivative terms gives a rate for 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. (orig.)