Determination of the pion-nucleon coupling constant from QCD sum rules

Abstract

We evaluate the πN coupling constant using a QCD sum rule based on the pion-to-vacuum matrix element of the correlator of two interpolating nucleon fields. The part of the correlator with Dirac structure kγ 5 is used, keeping all terms up to dimension 5 in the OPE and including continuum contributions on the phenomenological side. The ratio of this sum rule to the nucleon sum rule involving condensates of odd dimension yields stable resultswith values of g πn in the range 12±5. The sources of uncertainty are discussed.