γγ->π^0π^0 and η->π^0γγ at Low Energy Within the Extended Nambu Jon-Lasinio Model

Within the Extended Nambu Jona-Lasinio model, we calculate the O(p^6) counterterms entering the low-energy expansion of the γγ->π^0π^0 and the η->π^0γγ amplitudes in Chiral Perturbation Theory. For γγ -> π^0π^0 our results are compatible with both the experimental data and the two-loop calculation using meson resonance saturation. For the η decay we find γ(η->π^0γγ) = 0,58+-0,3 eV which is in agreement with experiment within one standard deviation. We also give predictions for the neutral pion polarizabilities and compare them with the results obtained from resonance saturation.