QCD with dynamical fermions

We present our latest hadron mass calculations for four flavors of staggered fermions on a 24 × 16³ lattice at quark mass ma = 0.010 and β = 5.35. Our work clearly shows a systematic tendency for the nucleon to ρ{variant} meson mass ratio to decrease below the naive quark model value of 3 2 as the zero quark mass limit is approached. This completes an extensive study of hadron spectroscopy using the pseudofermion method at numerous quark mass values for β = 5.20 and β = 5.35. We also present initial results of our new Hybrid Monte Carlo analysis at β = 5.35 and ma = 0.025 on the 24 × 16³ lattice. We discuss the performance of the algorithm on this lattice, and we measure hadron masses and the interquark potential. Where we can compare results, we find good agreement with our earlier pseudofermion calculations.