To the Lagrangian formulation of NJL model with separable interaction

A Lagrangian formulation of the Nambu-Jona-Lasinio model with separable interaction is given. The electromagnetic interaction is introduced in a non-minimal way to the nonlocal quark current. We have calculated the pion weak decay constant, the two-photon decay width, as well as the form factor of the γ*π0 -> γ-transition and the pion charge form factor. The two adjustable parameters, the range parameter appearing in the separable interaction and the constituent mass mq, have been fixed by fitting the experimental data for the pion decay constants