QCD beta function with two flavors of dynamical Wilson fermions.

We test the asymptotic scaling behavior of state-of-the-art simulations of QCD with two flavors of light Wilson fermions. This is done by matching {pi} and {rho} masses on lattices of size 16{sup 3}{times}32 and 8{sup 3}{times}16. We find that at {beta}=6/{ital g}{sup 2}=5.3 matching is not possible over a range extending down to {beta}=3.5. The large lattice data at {beta}=5.5 matches the small lattice values at {beta}=4.9(1) leading to a shift {Delta}{beta}=0.6(1), considerably larger than the perturbative prediction of 0.45. In both cases we conclude that the simulations are very far from the asymptotic scaling region. {copyright} {ital 1996 The American Physical Society.}