$\eta \to {\pi }^0\gamma \gamma$ decay in the three-flavor Nambu-Jona-Lasinio model

Y. Nemoto, M. Oka, M. Takizawa

We study the $\eta \to {\pi }^0\gamma \gamma$ decay via the quark-box diagram in the three-flavor Nambu--Jona-Lasinio model that includes the $U_A(1)$ breaking effect. We find that the $\eta$-meson mas…