Isoscalar axial-vector renormalization constant and polarized proton structure function

Abstract

The isoscalar axial-vector renormalization constant is reevaluated using the QCD sum-rule method. It is found to be substantially different from the anomaly-free octet axial-vector u^-γ_μγ₅₊d^-γ_μγ_5-2s^-γ_μγ₅ coupling. Combining this determination with the known values of the isovector coupling G_A and the F/D ratio for the octet current, we find the integral of the polarized proton structure function to be G_p=Fg₁^p(x)dx=0.135, in agreement with recent measurement by the European Muon Collaboration.