Isoscalar axial-vector renormalization constant and polarized proton structure function

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¯${\gamma }_{\mathrm{\mu }}$ ${\gamma }_{5+}$d¯${\gamma }_{\mathrm{\mu }}$ ${\gamma }_5$-2s¯${\gamma }_{\mathrm{\mu }}$ ${\gamma }_5$ 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 $G_p$=F $g_1^p$(x)dx=0.135, in agreement with recent measurement by the European Muon Collaboration.