2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/43219We study $ρ-ω-$interference by analyzing $J/ψ\to π^+π^-π^0π^0$. PDG-2002 data on $J/ψ$ decays into $PP$ and $PV$ ($P$ denotes pseudoscalar mesons; $V$, vector mesons) are used to fit a generic model which describes the $J/ψ$ decays. From the fits, we obtain anomalously large branching ratio $Br(ρ^0\to π^+π^-π^0)\sim 10^{-3}-10^{-2}$. A theoretical analysis for it is also provided, and the prediction is in good agreement with the anomalously large $Br(ρ^0\to π^+π^-π^0)$. By the fit, we also get the $η-η'-$mixing angle $θ=-19.68^o\pm 1.49^o$ and the constituent quark mass ratio $m_u/m_s\sim 0.6$ which are all reasonable.LaTeX file, no figure, to appear in the High Energe Phys and Nuclear Phys (Beijing)High Energy Physics - Phenomenologytext