Pion Loop Contribution to Rho-Omega Mixing and Mass Splitting
  We study the self-energy amplitudes for the rho-omega meson system produced by an effective field theory model at the quark level characterized by a finite range quark-quark interaction and an isospin breaking bare quark mass difference $m_u - m_d$. Dynamical effects associated with confinement and dressing of quarks and the finite size of the produced $\bar{q}q$ meson modes are treated. Parameters of this approach, previously constrained by soft pion physics, are here supplemented in a minimal way to reproduce $m_\omega$ and $g_{\rho\pi\pi}$. Calculations are carried out up to the one pion loop level and the predictions for rho-omega mixing, mass splitting, the rho width and the symmetry breaking omega-pi-pi coupling constant and form factor are presented. The contribution of the direct $\omega \rightarrow \pi\pi$ process relative to the $\omega \rightarrow \rho \rightarrow \pi\pi$ process is discussed within this model. 
K. L. Mitchell (TRIUMF) and P. C. Tandy (Kent State U.)