Isospin Breaking in $K_{\ell 4}$ Decays of the Charged Kaon

V. Cuplov, A. Nehme

The charged $K_{\ell 4}$ decay, $K^{+}\to {\pi }^{+}{\pi }^{-}{\ell }^{+}{\nu }_{\ell }$ is studied in the framework of chiral perturbation theory based on the effective Lagrangian including mesons, photons,…