Electromagnetic form factors in the Nambu-Jona-Lasinio model

The original Nambu-Jona-Lasinio model is treated to leading order in 1/N. The electromagnetic form factors of the constituent quarks and the pion, and the anomalous π0 → 2γ decay amplitude are obtained. Their dependence on the cutoff of the model is made explicit. Two distinct limits (depending on the ratio of the cutoff to the constituent quark mass) in which the cutoff can be taken to infinity are also discussed. We find that to leading order of 1/N the model in one limit corresponds to the linear and in the other to the nonlinear sigma model.