Antiproton-nucleon annihilations into three pions

Abstract

New data are presented for antiproton capture in deuterium for the reactions (a) $\overline{p}d\ensuremath{\rightarrow}2{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{p}_{s}$ at rest with spectator proton, (b)$\overline{p}d\ensuremath{\rightarrow}2{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{p}_{s}$ with the antiproton in flight (\ensuremath{\sim}0.35 GeV/c momentum), and (c)$\overline{p}d\ensuremath{\rightarrow}2{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}p$ at rest but with nonspectator protons. The striking features of the $2{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ Dalitz plot for (a) are compared with $\overline{p}p\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}$, ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ at rest, with $\overline{p}d\ensuremath{\rightarrow}2{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{p}_{s}$ at other energies, and with predictions of dual models. No consistent and satisfactory interpretation has been found. The possible quantum numbers of the $2{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ final state are discussed.