VIABILITY OF LATTICE PERTURBATION-THEORY

In this paper we show that the apparent failure of QCD lattice perturb ation theory to account for Monte Carlo measurements of perturbative q uantities results from choosing the bare lattice coupling constant as the expansion parameter. Using instead ''renormalized'' coupling const ants defined in terms of physical quantities, such as the heavy-quark potential, greatly enhances the predictive power of lattice perturbati on theory. The quality of these predictions is further enhanced by a m ethod for automatically determining the coupling-constant scale most a ppropriate to a particular quantity. We present a mean-field analysis that explains the large renormalizations relating lattice quantities, such as the coupling constant, to their continuum analogues. This sugg ests a new prescription for designing lattice operators that are more continuumlike than conventional operators. Finally, we provide evidenc e that the scaling of physical quantities can be asymptotic or perturb ative already at (quenched) beta's as low as 5.7, provided the evoluti on from scale to scale is analyzed using renormalized perturbation the ory. This result indicates that reliable simulations of QCD are possib le at these same low beta's.