Effects of the UA(1) anomaly on η → 2γ decay

We study the η → 2γ decay using an extended three-flavor Nambu-Jona-Lasinio model that includes the ʹt Hooft instanton induced interaction. The η meson mass and the η → 2γ decay width are reproduced simultaneously with a rather strong instanton induced interaction. The calculated η decay constant is fη = 2.23fπ and it suggests that the η meson is no longer a Goldstone boson.