QCD and resonance physics: The ϱ-ω mixing

The QCD-based approach to the resonance physics proposed earlier is extended to cover the ρ{variant}-ω mixing problem. We consider a two-point function relevant to the problem taking account of non-perturbative contributions. It is shown that virtual photon exchanges alone cannot explain the observed value of the mixing parameter. The phenomenon gets a natural explanation if one assumes a large isotopic symmetry violation in the mechanical quark masses, (m_d - m_u)/(m_d + m_u) ∼ 0.3. This number is close to that resulting from the well-known pseudoscalar meson analysis. Unlike the latter, however, our result does not assume an exact SU(3)_flavor symmetry in vacuum-to-vacuum matrix elements.