Search

The missing-mass technique has been used to study the spectra of neutral mesons produced by 2- and 3-Gev protons in the reaction $p+d\ensuremath{\rightarrow}{\mathrm{He}}^{3}+{x}^{0}$. Cross sections ($\frac{d\ensuremath{\sigma}}{{d\ensuremath{\Omega}}_{\mathrm{c}.\mathrm{m}.}}$) of about ${10}^{\ensuremath{-}34}$ ${\mathrm{cm}}^{2}$/sr were observed for the $\ensuremath{\pi}$, $\ensuremath{\eta}$, and $\ensuremath{\omega}$ for 3-GeV protons. A peak with a much smaller cross section was observed at a mass of 956 MeV. We have tentatively identified this peak as the ${\ensuremath{\eta}}^{\ensuremath{'}}$. Cross sections for the $\ensuremath{\pi}$ and $\ensuremath{\eta}$ were nearly a factor of 10 larger at 2 GeV than at 3 GeV. Deviations from simple phase space were observed near the two-pion threshold in both 2-GeV and 3-GeV data. Details of the experimental method and of the results are presented.