The field strength correlator from QCD sum rules

The gauge invariant two-point correlator for the gluon field strength tensor is analysed by means of the QCD sum rule method. To this end, we make use of a relation of this correlator to a two-point function for a quark-gluon hybrid in the limit of the quark mass going to infinity. From the sum rules a relation between the gluon correlation length and the gluon condensate is obtained