UA(1) symmetry breaking, scalar mesons and the nucleon spin problem in an effective 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-quark 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 pseudoscalar 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 between 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 effective 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-vector meson masses in general as well as in the tight-binding limit. (C) 2001 Elsevier Science B.V. All rights reserved.