A new global fit of the image at next-to-next-to-leading order in Chiral Perturbation Theory Original Research Article

A new fit is done to obtain numerical values for the order image low-energy-constants image in Chiral Perturbation Theory. This includes both new data and new calculated observables. We take into account masses, decay constants, image, ππ and πK scattering lengths and slopes and the slope of the pion scalar formfactor. We compare in detail where the changes w.r.t. the 10 years old “fit 10” come from. We discuss several scenarios for estimating the order image constants image and search for possible values of them that provide a good convergence for the ChPT series. We present two such sets. One big change is that the fits do not have the expected behaviour in the limit of large image as well as before.