Within the Extended Nambu Jona-Lasinio model, we calculate the O (p⁶) counterterms entering the low-energy expansion of the γγ->π⁰π⁰ and the η->π⁰γγ amplitudes in Chiral Perturbation Theory. For γγ -> π⁰π⁰ 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->π⁰γγ) = 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.
S. et al. (Wed,) studied this question.
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