
Matrix elements of fourquark operators are studied with two approaches. First inclusively; we consider twopoint functions of fourquark operators. We compute their corresponding spectral functions at very short distances using perturbative QCD with inclusion of O(alphas) corrections; and at very long distances, using the chiral effective realization of QCD in terms of Goldstone particles. A qualitative picture emerges which requires, for consistency between the two extreme behaviours, a large coupling constant for DELTAI = 1/2 transitions. The other, more direct approach, consists of calculating the effective action of fourquark operators by integrating out the quark fields in a gluonic background and in the presence of a source term which triggers spontaneous chiral symmetry breaking. The procedure follows the method elaborated recently in ref [1]. This way we compute the coupling constants of the lowestorder effective chiral lagrangian with DELTAS = 1 (DELTAI = 1/2 and 3/2) and DELTAS = 2 (the so called Bfactor.) The calculations include the wellknown O(N(c)2) contributions as well as the subleading O(N(c)) with inclusion of the O(alphas(N)c) terms. The picture which emerges at this approximation is already very encouraging. Comparison with other approaches is also made.
