A Dispersive Treatment of $K_{\ell 4}$ Decays

Gilberto Colangelo, Emilie Passemar, Peter Stoffer

$K_{\ell 4}$ are for several reasons an especially interesting decay channel of $K$ mesons: $K_{\ell 4}$ decays allow an accurate measurement of a combination of $S$-wave $\pi \pi$ scatte…