h-Meson Decays and Strong UA(1) Breaking in the Three-flavour Nambu–Jona-Lasinio Model

Abstract

We study the η → γγ and η → π ⁰γγ decays using an extended three-flavour Nambu–Jona-Lasinio model that includes the ’t Hooft instanton induced interaction. We find that the η-meson mass, the η → γγ decay width and the η → π ⁰γγ decay width are in good agreement with the experimental values when the U_A(1) breaking is strong and the flavour SU(3) singlet-octet mixing angle θ is about zero. The effects of the U_A(1) breaking on the baryon number one and two systems are also studied.