$K_{l4}$ at two-loops and CHPT predictions for $\pi\pi$-scattering

Abstract

We present the results from our two-loop calculations of masses, decay-constants, vacuum-expectation-values and the $K_{\ell4}$ form-factors in three-flavour Chiral Perturbation Theory (CHPT). We use this to fit the $L_i^r$ to two-loops and discuss the ensuing predictions for $\pi\pi$-threshold parameters.