Mixed Quark-Gluon Condensate Beyond Chiral Limit

Using the Dyson-Schwinger equation and perturbation theory, we calculate the mixed quark-gluon condensates in the chiral limit and in the case of nonzero quark current mass for the light quark u/d and strange quark s. The results show that the mixed quark-gluon condensate will decrease when the quark mass increases. For the quark with zero mass, we obtain m(0)(2)= g <(q) over bar sigma(mu nu) G(mu nu)q >/<(q) over barq > congruent to 0.68 GeV2, which is in good agreement with the QCD sum rules estimate m(0)(2) = (0.8 +/- 0.2) GeV2.