Lattice QCD with 0, 2 and 4 quark flavors

We have done simulations of lattice QCD with different numbers of light dynamical quarks. Since we cannot reach the continuum limit with our current computers, we have done comparisons with 0 (quenched), 2 and 4 light quark flavors with the physical volume and lattice spacing constant, when these are determined from the mass of the rho. We find a 7% (2 standard deviation) difference in the nucleon to rho mass ratio for 2 and 4 quarks. More importantly, the effects of chiral symmetry breaking are dramatically decreased for the case of 4 light quarks.