New Analysis of the Delta I = 1/2 Rule in the 1/Nc 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/Nc 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/Nc 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.
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