Lattice measurements of nonlocal quark condensates, vacuum correlation length, and pion distribution amplitude in QCD

Recent data from lattice measurements of gauge-invariant nonlocal scalar quark condensates are analyzed to extract the short-distance correlation length 1/lambda(q) and to construct an admissible Ansatz for the condensate behavior in a coordinate space. The correlation length values for both the quenched and full-QCD cases appear in good agreement with the well-known QCD sum-rule (SR) estimates of the mixed quark-gluon condensate 2lambda(q)(2)=[(q) over bar (igsigma(munu)G(munu))q]/[(q) over barq]=0.8-1.1 GeV2. We test two different Ansatze for a nonlocal quark condensate and trace their influence on the twist-2 pion distribution amplitude by means of QCD SR's. The main features of the pion distribution amplitude are confirmed by the CLEO experimental results.