Update on pi and K Physics

University of California; Santa Barbara, California, USAE-mail:sugar@physics.ucsb.eduWe present an update of the MILC studies of the physics of light pseudoscalars using improvedstaggered fermions. New runs at lighter quark mass, as well as increased statistics for oldersets, are enabling us to improve the results for decay constants in full QCD. In addition, wehave analyzed quenched runs at two different lattice spacings. This makes possible a test of theapplicability of staggered chiral perturbation theory in a different context.XXIIIrd International Symposium on Lattice Field Theory25-30 July 2005Trinity College, Dublin, Ireland