Singlet axial-vector coupling constant of the nucleon in QCD without instantons

We have analyzed axial-vector current–current correlation functions between one-nucleon states to calculate the singlet axial-vector coupling constant of the nucleon. The octet–octet and the octet–singlet current correlators, investigated in this work, do not require any use of instanton effects. The QCD and hadronic parameters used for the evaluation of correlators have been varied by (10–20)%. The value of the singlet axial-vector coupling constant of the nucleon obtained from this analysis is consistent with its current determination from experiments and QCD theory.