Two photons decay of the glueball and scalar isoscalar mesons in a scaled NJL model

We use a modified version of the Nambu--Jona-Lasinio model which implements the QCD trace anomaly to calculate the two photons decay width of the glueball (f_0(1500)) and of the two scalar mesons (f_0(1370), f_{J=0}(1710)) to which it is mixed. We investigate the effect of this mixing over the coupling constants of the f_0 states to the quarks.