Taking the gauge invariant quark correlator as an example, in this work weperform a direct comparison of lattice QCD simulations with the QCD sum ruleapproach. The quark correlator is first investigated in the framework of QCDsum rules and the correlation length of the quark field is calculated.Comparing the phenomenological part of the sum rule with previous measurementsof the quark correlator on the lattice, we are able to obtain an independentresult for the correlation length. From a fit of the lattice data to theoperator product expansion, the quark condensate and the mixed quark-gluoncondensate can be extracted.
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