The QCD chiral condensate from the lattice

We determine the chiral condensate from simulations of quenched lattice QCD with Wilson fermions. Our measurements have been obtained with high statis tics at three values of the gauge coupling, corresponding to UV cutoffs in the range 2-4 GeV. Several improvements have been made with respect to earl ier lattice computations. The most important are the non-perturbative renor malization of the condensate, the use of the tree-level improved Clover act ion and the reduction of the systematic error due to uncertainties in the l attice calibration. Our result for the chiral condensate in the <(MS)over b ar> scheme is (<(psi)over bar>psi)(<(MS)over bar>) (mu = 2 GeV) = -0.0147(8 )(16)(12) GeV3 = -[245(4)(9)(7) MeV](3), where the first error is statistic al, the second is due to the nonperturbative renormalization and the third due to the lattice calibration. (C) 1999 Elsevier Science B.V.