CHIRALLY SYMMETRICAL O(1 N-C) CORRECTIONS TO THE NAMBU-JONA-LASINIO MODEL/

(W)e develop an extended chirally symmetric self-consistent approximat ion scheme to the Nambu-Jona-Lasinio model, that corresponds to O(1/N- C) corrections to the usual Hartree + random phase approximations. Thi s scheme amounts to adding ''meson cloud'' contributions self-consiste ntly to the quark self-energy and the meson polarization functions in a manner suggested by the weakly interacting nature of the quark and c ollective meson degrees of freedom of the NJL model in the large N-C l imit. We demonstrate explicitly that this scheme fulfills all the chir al symmetry theorems, namely the Goldstone theorem, the Goldberger-Tre iman relation, and the conservation of the quark axial current. We exp lore the corrections to the quark self-energy and scalar condensate, a s well as to the pion polarization function and the weak decay constan t f(pi). The numerical evaluation of these corrections is presented an d discussed. (C) 1995 Academic Press, Inc.