Neutral Kaon Decays into Lepton Pairs

The decay modes ${K_1}^0\to {\mu }^{+}{\mu }^{-}$ and ${K_2}^0\to {\mu }^{+}{\mu }^{-}$ are discussed within the framework of first-order weak combined with fourth-order electromagnetic interactions. The possibility of obtaining lower bounds to the corresponding decay rates is examined, and estimates of the lower bounds are given in a perturbation-theory model. Possible enhancement effects due to strong interactions have been estimated through a simple model of final-state interactions. The assumption of $\mathrm{CP}$ invariance is made throughout.