Light pseudoscalar decay constants, quark masses, and low energy constants from three-flavor lattice QCD

As part of our program of lattice simulations of three-flavor QCD with improved staggered quarks, we have calculated pseudoscalar meson masses and decay constants for a range of valence quark masses and sea-quark masses on lattices with lattice spacings of about 0.125 and 0.09 fm. We fit the lattice data to forms computed with ‘‘staggered chiral perturbation theory.'' Our results provide a sensitive test of the lattice simulations, and especially of the chiral behavior, including the effects of chiral logarithms. We find: frr= 129.5 + 0.9 + 3.5 MeV, fK = 156.6 + 1.0 + 3.6 MeV, and fK/frr = 1.210(4)(13), where the errors are statistical and systematic.