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 statistics 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 earlier lattice computations. The most important are the non-perturbative renormalization of the condensate, the use of the tree-level improved Clover action and the reduction of the systematic error due to uncertainties in the lattice calibration. Our result for the chiral condensate in the <(MS)over bar> 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 statistical, the second is due to the nonperturbative renormalization and the third due to the lattice calibration. (C) 1999 Elsevier Science B.V.