Quark Virtuality and QCD Vacuum Condensates

Based on the Dyson--Schwinger equations (DSEs) in the `rainbow' approximation, we investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, we calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λ ²_u,d = 0.7GeV² for u,d quarks, and λ ²_s = 1.6GeV² for s quark. Our theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions.