UA(1) symmetry breaking quark interactions from vacuum polarization

By considering the one loop background field method for a quark-antiquark interaction mediated by one (non perturbative) gluon exchange, sixth order quark effective interactions are derived and investigated in the limit of zero momentum transfer. They extend fourth order quark interactions worked out in previous works of the author. These interactions break UA(1) symmetry and may be either momentum independent or dependent. Part of these UA(1) breaking interactions vanish in the limit of massless quarks and several other - involving vector and/or axial quark currents - survive even in the absence of Dynamical Symmetry Breaking. By means of the auxiliary field method, these interactions give rise to three meson interactions whose values are compared to phenomenological values found in the literature. By restricting to the up and down quark sector, some three-meson couplings correspond to the strong decay of specific light axial-vector mesons. These (strong) decays are shown to yield an asymmetry in the production rate of positive and negative pions by means of interference effects that arise due to neutral meson mixings.