Nonperturbative improvement and tree-level correction of the quark propagator - art. no. 074508

We extend an earlier study of the Landau gauge quark propagator in quenched QCD where we used two forms of the O(a)-improved propagator with the Sheik holeslami-Wohlert quark action. In the present study we use the nonperturba tive value for the clover coefficient c(sw) and mean-field improvement coef ficients in our improved quark propagators. We compare this with our earlie r results which used the mean-field c(sw) and tree-level improvement coeffi cients for the propagator. We also compare three different implementations of tree-level correction: additive, multiplicative, and hybrid. We show tha t the hybrid approach is the most robust and reliable and can successfully deal even with strong ultraviolet behavior and zero crossing of the lattice tree-level expression. We find good agreement between our improved quark p ropagators when using the appropriate nonperturbative improvement coefficie nts and hybrid tree-level correction. We also present a simple extrapolatio n of the quark mass function to the chiral limit.