Fitting the pion and kaon mass and decay constant to lattice data

Abstract: We use lattice QCD data to perform a fit of the pion and kaon mass and decay constant to next-to-next-to-leading order (NNLO) in three-flavor Chiral Perturbation Theory (ChPT). To improve our fits, we make use of finite volume corrections at both one- and two-loop order. This turns out to provide a small but noticeable improvement of our fits. Our fits see a significant improvement with the inclusion of NNLO terms, but we obtain values that differ from our expectations for the low-energy constants (LECs). We find that more lattice data with smaller kaon masses is needed in order to make any conclusions regarding the range of applicability for three-flavor ChPT.