Weak-ElectromagneticK-Meson Decays

Abstract

We discuss the contributions of the combined first-order-weak plus higher-order-electromagnetic effects to several $K$-meson decays. It is shown that if one uses a chiral SU(3) ×SU(3) pole model to explain both $K_S\to 2\pi$ and $K_L\to 2\gamma$ one needs an effective nonleptonic interaction Lagrangian which contains 8, and 27, $\Delta I=\frac{1}{2}$ pieces. This gives results for $K^{+}\to {\pi }^{+}l\overline{l}$ compatible with the experimental data. We also calculate within this model the real part of the $K_L\to l\overline{l}$ amplitude, which results in a very small contribution to the decay rate.