CALCULATION OF THE 4-QUARK CONDENSATES IN THE QCD MOTIVATED NAMBU-JONA-LASINIO MODEL

The four-quark condensates appearing in the QCD sum rule are calculate d nonperturbatively in a realistic QCD motivated Nambu-Jona-Lasinio mo del. The calculation is in the framework of the effective potential fo r local composite operators up to next-to-the-leading order in the 1/N expansion (N = N-c = N-f) in which the non-factorized parts of the co ndensates are included. The enhancement factor K defined in the phenom enological analysis is calculated as the contribution of the non-facto rized parts of the four-quark condensates. The obtained kappa is not l arge enough to account for the phenomenological value kappa = 2.4.