Pion observables in the extended NJL model with vector and axial-vector mesons

The momentum-space bosonization method of a Nambu and Jona-Lasinio type model with vector and axial-vector mesons is applied to pi pi scattering. Unlike the case in earlier published papers, we obtain the pi pi scattering amplitude using the linear and nonlinear realizations of chiral symmetry and Fully taking into account the momentum dependence oi meson vertices. We show the full physical equivalence between these two approaches. The chiral expansion procedure in this model is discussed in detail. Chiral expansions of the quark mass, pion mass and constant f(pi) are obtained. The low-energy pi pi phase shifts are compared to the available data. We also study the scalar form factor of the pion. (C) 1996 Academic Press, Inc.