Non-perturbative results for the coefficients bm and bA-bP in O(a) improved lattice QCD

We determine the improvement coefficients b(m) and b(A) - b(P) in quenched lattice QCD for a range of beta -values, which is relevant for current large scale simulations. At fixed beta, the results are rather sensitive to the precise choices of parameters. We therefore impose improvement conditions at constant renormalized parameters, and the coefficients are then obtained as smooth functions of g(0)(2). Other improvement conditions yield a different functional dependence, but the difference between the coefficients vanishes with a rate proportional to the lattice spacing. We verify this theoretical expectation in a few examples and are therefore confident that O(a) improvement is achieved for physical quantities. As a byproduct of our analysis we also obtain the finite renormalization constant which relates the subtracted ban quark mass to the bare PCAC mass. (C) 2001 Elsevier Science B.V. All rights reserved.