A new global fit of the Lir at next-to-next-to-leading order in Chiral Perturbation Theory

A new fit is done to obtain numerical values for the order p4p4 low-energy-constants Lir in Chiral Perturbation Theory. This includes both new data and new calculated observables. We take into account masses, decay constants, Kℓ4Kℓ4, 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 p6p6 constants Cir 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 NcNc as well as before.