GAMMA-GAMMA-]PI(0)PI(0) AND ETA-]PI(0)GAMMA-GAMMA AT LOW ENERGY WITHIN THE EXTENDED NAMBU JONA-LASINIO MODEL

摘要

Within the Extended Nambu Jona-Lasinio model. we calculate the O(p(6)) counterterms entering the low-energy expansion of the gamma gamma --> pi(0) pi(0) and the eta --> pi(0) gamma gamma amplitudes in Chiral Perturbation Theory. For gamma gamma --> pi(0) pi(0) our results are compatible with both the experimental data and the two-loop calculation using meson resonance saturation. For the eta decay we find Gamma(eta --> pi(0) gamma gamma) = 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. [References: 44]