U-A(1) symmetry breaking, scalar mesons and the nucleon spin problem in aneffective chiral field theory

We establish a relationship between the scalar-meson spectrum and the U-A(1 ) symmetry-breaking 't Hooft interaction on one hand and the constituent-qu ark flavor singlet axial coupling constant g(A,Q)((0)) on the other, using an effective chiral quark field theory. This analysis leads to the new sum rule g(A,Q)((0))[m(eta')(2) + m(eta)(2) - 2m(K)(2)] similar or equal to -m( f0')(2) -m(f0)(2) + 2m(k0)*(2), where eta', eta, K are the observed pseudos calar mesons, K-0* is the strange scalar meson at 1430 MeV and f(0), f(0)' are "the eighth and the ninth" scalar mesons. We discuss the relationship b etween the constituent-quark flavor singlet axial coupling constant g(A,Q)( (0)) and the nucleon one g(A,N)((0)) ("nucleon spin content") in this effec tive field theory. We also relate g(A,Q)((0)) as well as the flavour octet constituent-quark axial coupling constant g(A,Q)((0)) to vector and axial-v ector meson masses in general as well as in the tight-binding limit. (C) 20 01 Elsevier Science B.V. All rights reserved.