THE DELTA-I=1 2 RULE AND (B)OVER-CAP-B-K AT O(P(4)) IN THE CHIRAL EXPANSION/

yWe calculate the hadronic matrix elements to O(p(4)) in the chiral ex pansion for the (Delta S = 1) K-0 --> 2 pi decays and the (Delta S = 2 ) <(K)over bar (0)> - K-0 oscillation, This is done within the framewo rk of the chiral quark model, The chiral coefficients thus determined depend on the values of the quark and gluon condensates and the consti tuent quark mass, We show that it is possible to fit the Delta I = 1/2 rule of kaon decays with values of the condensates close to those obt ained by QCD sum rules. The renormalization invariant amplitudes are o btained by matching the hadronic matrix elements and their chiral corr ections to the short-distance NLO Wilson coefficients. For the same in put values, we study the parameter (B) over cap(K)$ of kaon oscillatio n and find (B) over cap(K)$ = 1.1 +/- 0.2. As an independent check, we determine (B) over cap(K)$ from the experimental value of the K-L-K-S mass difference by using our calculation of the long-distance contrib utions. The destructive interplay between the short-and long-distance amplitudes yields (B) over cap(K)$ = 1.2 +/- 0.1, in agreement with th e direct calculation. (C) 1998 Elsevier Science B.V.