Strong $U_A(1)$ breaking in radiative $\eta$ decays

Abstract

We study the \egg, \egm and \epg decays using an extended three-flavor Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced interaction. We find that the $\eta$-meson mass, the \egg, \egm and \epg decay widths are in good agreement with the experimental values when the $U_A(1)$ breaking is strong and the flavor $SU(3)$ singlet-octet mixing angle $\theta$ is about zero. The calculated $\eta \gamma {\gamma }^{\ast }$ transition form factor has somewhat weaker dependence on the squared four-momentum of the virtual photon. The effects of the $U_A(1)$ anomaly on the scalar quark contents in the nucleon, the ${\Sigma }_{\pi N}$ and ${\Sigma }_{KN}$ terms and the baryon number one and two systems are also studied.

41 pages, LaTeX, 17 eps figures, uses epsf.sty and cite.sty

References in corpus (8)

• QCD Phenomenology based on a Chiral Effective Lagrangian
• The ratios of the light quark masses
• The instanton liquid in QCD at zero and finite temperature
• The $\gamma \gamma \to {\pi }^0{\pi }^0$ and $\eta \to {\pi }^0\gamma \gamma$ Transitions in the Extended NJL Model
• $\gamma \gamma \to {\pi }^0{\pi }^0$ and $\eta \to {\pi }^0\gamma \gamma$ at low energy within the Extended Nambu Jona-Lasinio Model
• $\eta \to {\pi }^0\gamma \gamma$ decay in the three-flavor Nambu-Jona-Lasinio model
• $\eta \to {\pi }^0\gamma \gamma$ and $\gamma \gamma \to {\pi }^0{\pi }^0$ in $O(p^6)$ chiral perturbation theory
• $\eta \to {\pi }^0\gamma \gamma$ to $\mathcal{O}(p{)}^6$ in Chiral Perturbation Theory

Cited by in corpus (15)

• η- and η'-mesic nuclei and U_A(1) anomaly at finite density
• Radiative Decays, Nonet Symmetry and SU(3) Breaking
• Analysis of U${}_A$(1) symmetry-breaking and restoration effects on the scalar-pseudoscalar spectrum
• Topological susceptibility at zero and finite temperature in the Nambu-Jona-Lasinio model
• eta and eta' in a coupled Schwinger-Dyson and Bethe-Salpeter approach
• Light Scalar Mesons in the Improved Ladder QCD
• Meson-baryon couplings and the $F/D$ ratio from QCD sum rules
• Anomalous decay of pion and eta at finite density
• Search for the radiative decay $\eta \to {\pi }^0\gamma \gamma$ in the SND experiment at VEPP-2M
• Effects of the Regularization on the Restoration of Chiral and Axial Symmetries
• Effects of Instanton Induced Interaction on the Pentaquarks
• Role of U${}_A$(1) breaking term in dynamical chiral symmetry breaking of chiral effective theories
• U_A(1) Symmetry Breaking and eta, eta prime mesons in the Bethe-Salpeter Approach
• Anomalous decay of pion and eta at finite temperature
• Finite Quark Mass Effects in the Improved Ladder Bethe-Salpeter Amplitudes