New Analysis of the Delta I = 1/2 Rule in the 1/N_c Expansion for K --> pi pi Decays

Abstract

We analyze long-distance contributions to the K --> pi pi amplitudes relevant for the Delta I = 1/2 selection rule in the framework of the 1/N_c expansion. We use a modified prescription for the identification of meson momenta in the chiral loop corrections to gain a consistent matching with the short-distance part. Our approach involves a separation of non-factorizable and factorizable 1/N_c corrections. Along these lines we calculate the one-loop contributions from the lowest order lagrangian. Our main result is an additional enhancement of the Delta I = 1/2 channel amplitude which we find in good agreement with experiment.

Comments: 10 pages, 4 eps figures. Talk presented at the XXIth School of Theoretical Physics "Recent Progress in Theory and Phenomenology of Fundamental Interactions", Ustroń, Poland, September 19-24, 1997. Two typos in Eq. (17) and Eq. (18) have been corrected