Observation ofρ−ωInterference in Antiproton Annihilations

Evidence for structure near the ${\omega }^0$ mass in the (${\pi }^{+}{\pi }^{-}$) mass spectrum from the reaction $\overline{p}p\to 2{\pi }^{+}2{\pi }^{-}$, at incident momenta from 1.26 to 1.65 GeV/c, is presented. We interpret this structure as arising from $\rho -\omega$ interference in the $2\pi$ decay mode, with a statistical significance of about 3.5 standard deviations. The effect can be well fitted by a partial width $\Gamma (\omega \to 2\pi )$ in the range 0.18 to 5.3 MeV (95% confidence level). Alternatively, if $\Gamma (\omega \to 2\pi )$ is taken from $e^{+}{e}^{-}$ colliding-beam results, our data can be used to study both the relative phase and coherence of $\rho$ and $\omega$ production in $\overline{p}p$ annihilation.