Pion-Pion Interaction in the Reactionp¯+p→2π++2π−+nπ0

Deviations from the expected two-pion effective-mass distributions have been found in the reaction $\overline{p}+p\to 2{\pi }^{+}+2\mathrm{}{\pi }^{-}+n{\pi }^0$. These occur in two regions, 300 Mev and 750 Mev, and could be explained by the $T=0\mathrm{}$, pion-pion interaction reported by Abashian, Booth, and Crowe and the widely observed $\rho$ meson ($T=1\mathrm{}$, $J=1^{-}$ pion-pion resonance). The data in the 750-Mev region for ${\pi }^{+}{\pi }^{-}$ combinations ($Q=0\mathrm{}$) show an apparent double-peak structure—one at 720 Mev ($\Gamma =20\mathrm{}$ Mev), the other at 780 Mev ($\Gamma =60\mathrm{}$ Mev). However, the $\mathrm{}\left|Q\right|=1\mathrm{}$ data (${\pi }^{+}{\pi }^0$ and ${\pi }^{-}{\pi }^0$ combinations) are consistent with the previously observed single $T=1\mathrm{}$, $J=1^{-}$ resonance. Our data give $M_{\rho }=767\mathrm{}$ Mev ($\Gamma =110\mathrm{}$ Mev). As these parameters also fit the $Q=0\mathrm{}$ data, a detailed discussion of the statistical significance of the one-peak and two-peak hypotheses is given. A search has been made for possible neutral modes of decay of the heavy mesons, and no evidence has been found.