Nonlocal gluon condensates in QCD sum rules

Nonlocal gluon condensates are vacuum expectations of the product of gluon field strength tensors. Short-distance expansions of two-, three-, and four-gluon condensates are presented up to dimension-eight local operators. We propose a method for calculating the Wilson coefficients based on the presented expansions and the Feynman diagram technique in the background field approach. The method is demonstrated using the glueball current correlators as examples. Methodological aspects of the background field approach are discussed in relation to glueball studies within QCD sum rules. We confirm the results for operator product expansion of the two-gluon 0f+ glueball current correlators and calculate additional contributions coming from dimension-six four-quark condensate and dimension-eight mixed quark-gluon condensates. The operator product expansions used in QCD sum rules for three-gluon 0f+ glueballs are revisited up to dimension-six order.

Automated summary

This article presents a method for expanding nonlocal gluon condensates and discusses their application in the background field approach. It also calculates additional contributions to glueball current correlators.