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) \ifmmode\times\else\texttimes\fi{}SU(3) pole model to explain both ${K}_{S}\ensuremath{\rightarrow}2\ensuremath{\pi}$ and ${K}_{L}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ one needs an effective nonleptonic interaction Lagrangian which contains 8, and 27, $\ensuremath{\Delta}I=\frac{1}{2}$ pieces. This gives results for ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}l\overline{l}$ compatible with the experimental data. We also calculate within this model the real part of the ${K}_{L}\ensuremath{\rightarrow}l\overline{l}$ amplitude, which results in a very small contribution to the decay rate.