Precise Determination of|Vus|from Lattice Calculations of Pseudoscalar Decay Constants

Abstract

Combining the ratio of experimental kaon and pion decay widths, Gamma(K-->munu (mu)(gamma))/Gamma(pi-->munu (mu)(gamma)), with a recent lattice gauge theory calculation of f(K)/f(pi) provides a precise value for the Cabibbo-Kobayashi-Maskawa quark mixing matrix element |V(us)|=0.2219(25) or if three generation unitarity is assumed |V(us)|=0.222 1(24). Comparison with other determinations of that fundamental parameter, implications, and an outlook for future improvements are given.