Study of the Reactionsπ−p→pπ−MM0andπ−p→pπ+π−π−MM0at 8 GeV/c

Results are presented from a hydrogen-bubble-chamber study of the final states $p{\pi }^{-}\mathrm{M}{\mathrm{M}}^0$ and $p{\pi }^{+}{\pi }^{-}{\pi }^{-}\mathrm{M}{\mathrm{M}}^0$, where M${\mathrm{M}}^0$ represents a neutral boson state of mass $\ge 2m\left({\pi }^0\right)$. The proton was identified by ionization for all events in the sample. Production of ${\eta }^0$, ${\omega }^0$, and $f^0$ mesons with decays into all neutral particles is observed in the $p{\pi }^{-}\mathrm{M}{\mathrm{M}}^0$ final state. Peaks are observed in the ${\eta }^0{\pi }^{-}$ spectrum at 1080 and 1310 MeV. The higher-mass peak has mass 1306±8 MeV and width ${41}_{-16\mathrm{}}^{+20\mathrm{}}$ MeV and is identified as the $A_2$. The branching ratio for $\frac{A_2\to {\eta }^0{\pi }^{-}}{A_2\to {\left(\rho \pi \right)}^{-}}$ has been measured as (18±7)%. There is no evidence for a 980-MeV ${\eta }^0{\pi }^{-}$ enhancement. Data on the $p{\pi }^{+}{\pi }^{-}{\pi }^{-}\mathrm{M}{\mathrm{M}}^0$ final state show evidence for ${\eta }^0$ and ${\omega }^0$ production.