Axial-vector coupling constants and chiral-symmetry restoration

The isovector axial-vector coupling constant gA is determined by using the method of QCD sum rules. A sum rule for (gA-1) is obtained, and it is shown that, with standard values of the quark condensates, gA=1.26±0.08. It is also shown that the isovector axial-vector coupling (gA-1)=0 in the limit in which chiral symmetry is restored, and the quark condensate vanishes. A sum rule is also obtained for the ''isoscalar'' axial-vector coupling constant gAS, which is found to be 0.13 if the isovector values of susceptibilities are used. On the other hand, gAS=-0.68 if the quark condensate is set to zero while gAS=-1.00 if both the quark and gluon condensates vanish in the event of chiral-symmetry restoration. The values of gA and gAS allow us to deduce Δu and Δd in the proton