Investigations on the Property of $f_0(600)$ and $f_0(980)$ Resonances in $\gamma \gamma \to \pi \pi$ Process

Using dispersion relation technique and experimental data, a coupled channel analysis on $\gamma \gamma \to \pi \pi$ process is made. Di-photon coupling of $f_0(600)$ and $f_0(980)$ resonances are extracted and their dynamical properties are discussed. Especially we study the physical meaning of the coupling constant $g_{\sigma \pi \pi }^2$, which maintains a negative real part as determined through dispersive analyses.