Continuum limit of lattice QCD with staggered quarks in the quenched   approximation - a critical role for the chiral extrapolation
  We calculate the light quark spectrum of lattice QCD in the quenched approximation using Kogut-Susskind quarks. By combining results for different lattice spacings, several volumes and five quark masses, we are able to take the light quark mass, infinite volume, continuum limit. When we use non-linear chiral extrapolations, we find that the nucleon to rho mass ratio is 1.254 +- 0.018 +- 0.027, where the errors are statistical and systematic (within the quenched approximation), respectively. This should be compared with the experimental value of 1.22. Our results indicate that the error due to quenching is less than about 5%. 
MILC Collaboration: Claude Bernard, Tom Blum, Carleton DeTar, Steven   Gottlieb, Urs M. Heller, James E. Hetrick, Craig McNe...