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

The S-wave ππ scattering lengths a0 and a2 are calculated to the lowest order of 1/Nc expansion in the general framework of SU(2) NJL model beyond mean-field approximation. It is shown that using the universal curve of a0 and a2 the four NJL parameters, i.e., the current quark mass m0, the four fermion coupling constant G, the quark momentum cut-off Λf and the meson momentum cut-off Λb, also the S-wave ππ scattering lengths in NJL model can be determined.