S-wave pi pi scattering lengths in the SU(2) NJL model beyond mean-field approximation

The S-wave pi pi scattering lengths a(o) and a(2) are calculated to the low est order of 1/N-c expansion in the general framework of SU(2) NJL model be yond mean-field approximation. It is shown that using the universal curve o f a(o) and a(2) the four NJL parameters, i.e., the current quark mass m(o), the four fermion coupling constant G, the quark momentum cut-off Lambda(f) and the meson momentum cut-off Lambda(b), also the S-wave pi pi scattering lengths in NJL model can be determined. (C) 1999 Published by Elsevier Sci ence B.V. All rights reserved.