The Decays $K\to \pi {\ell }^{+}{\ell }^{-}$ beyond Leading Order in the Chiral Expansion

G. D'Ambrosio, G. Ecker, G. Isidori +1

We present a model-independent analysis of $K^{+}\to {\pi }^{+}{\ell }^{+}{\ell }^{-}$ and $K_S\to {\pi }^0{\ell }^{+}{\ell }^{-}$ decays, including $K\to 3\pi$ unitarity corrections and a general decomposition of the…