Rare kaon decays revisited

We present an updated discussion of K --> pi(l) over barl decays in a combined framework of chiral perturbation theory and large-N-c QCD, which assumes the dominance of a minimal narrow resonance structure in the invariant mass dependence of the (l) over barl pair. The proposed picture reproduces very well, both the experimental K+ --> pi(+)e(+)e(-) decay rate and the invariant e(+)e(-) mass spectrum. The predicted Br(K-S --> pi(0)e(+)e(-)) is, within errors, consistent with the recently reported result from the NA48 Collaboration. Predictions for the K --> pimu(+)mu(-) modes are also obtained. We find that the resulting interference between the direct and indirect CP-violation amplitudes in K-L --> pi(0)e(+)e(-) is constructive. (C) 2004 Elsevier B.V. All rights reserved.