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.

The “Rutgers Annihilation Spectrometer” (RAS) measures cross sections for antiproton annihilations as a function of the pp mass, final-state multiplicities, and degree of non-peripheralism, with a resolution of ±5 MeV and typical statistics of 10 6 events per mass bin 5 MeV wide. The non-annihilation events are suppressed by anticoinciding the events in which charged particles are emitted within the forward cones defined by the lab polar angles 2 1 2 °, 5°, 10° and 20° (4 “degrees of non-peripheralism”), eliminating single meson exchange mechanisms which are non-resonant and highly peripheral. Measurements are done at 7 incident a momenta simultaneously. Scintillation counters are the only detectors used. On-line data acquisition is accomplished by a hard-wired electronic processor (“MEGAHPOL”) capable of sorting data on 100 000 incident antiprotons per second.