The Delta I=1/2 rule in kaon decays: A new look

The K --> pi pi decay amplitudes are studied within the framework of genera lized factorization, in which the effective Wilson coefficients are gauge-i nvariant, renormalization-scale and -scheme independent, while factorizatio n is applied to the tree-level hadronic matrix elements. Nonfactorized cont ributions to the hadronic matrix elements of(V - A)(V - A) four-quark opera tors, which are needed to account for the suppression of the Delta I = 3/2, K --> pi pi amplitude A(2) and the enhancement of the Delta I = 1/2, A(o) amplitude, are phenomenologically extracted from the measured K+ --> pi(+)p i(o) decay and found to be large. The A(o)/A(2) ratio is predicted to lie i n the range 15-17 for m(s)(1 GeV) = (127 - 150) MeV. Vertex and penguin-typ e radiative corrections to the matrix elements of four-quark operators and nonfactorized effects due to soft-gluon exchange account for the bulk of th e Delta I = 1/2 rule. A comparison of the present analysis with the chiral- loop approach is given.