The UA(1) problem and the role of correlated q qbar exchange in effective theories of QCD

Abstract

The combined absence of physical realizations of the UA(1) symmetry possessed by the classical QCD action in the chiral limit, and of an isoscalar Goldstone boson associated with its spontaneous breakdown, has been dubbed the UA(1) problem. A formal resolution of this problem proposed by 't Hooft relies on instantons to provide a mass to the would-be Goldstone boson (eta '). An alternate scheme for the generation of an eta ' mass proposed by Kogut and Susskind derives from quark annihilation into gluons and a strong infrared singularity in the gluon propagator associated with confinement. We demonstrate here how such diagrams are generated in quark based effective theories by including a certain class of diagrams which arise from correlated q qbar exchange and are of higher order 1/N_c. A low energy energy expansion of this corrections is of the form discussed by Witten, di Vecchia and Veneziano.

Detailed analysis of multigluon annihilation diagrams and wave function renormalization added, 19 pages (REVTEX) + 5 figures (PostScript), PRC in print

References in corpus (2)

• Hadron Physics from the Global Color Model of QCD
• The mixed quark-gluon condensate from an effective quark-quark interaction

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• Tensor susceptibility of the QCD vacuum from an effective quark-quark interaction
• Pion-nucleon scattering and the nucleon sigma term in an extended sigma model
• QCD and the eta prime Mass: Instantons or Confinement?
• K -> pi pi and a light scalar meson
• U_A(1) Symmetry Breaking and eta, eta prime mesons in the Bethe-Salpeter Approach