KL,S → l+l− decays in the quark model of superconductivity type

Abstract

The probabilities of KL,S → l+l− decays are calculated by considering only the dominant two-lepton channel KL,S →γ*γ* → l+l−. The transitions K0 → X, where X=π0,η,η′ orɛ (700) dominating in the KL,S →γ*γ*decay amplitudes, are described by the effective weak Lagrangian. The matrix elements of four-quark operators are calculated within the framework of the quark model of superconductivity type. It is shown that the leading contribution to matrix elements of K0 → X transitions comes from the penguin operator matrix elements.