Missing-Mass Spectra Produced by 2-GeV Protons in the Reactionp+d→He3+X0

We investigated the missing-mass spectra at the $2\ensuremath{\pi}$ threshold in the reaction $p+d\ensuremath{\rightarrow}{\mathrm{He}}^{3}+{X}^{0}$ and searched for the resonance reported at a mass of 450 MeV using 2-GeV protons. The shape of the missing-mass spectra below the ${\ensuremath{\eta}}^{0}$ mass deviates from two-body phase space and was similar to that obtained with 3-GeV protons. If a 450-MeV resonance exists, the c.m. cross section for producing it in this reaction is less than 10.8 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}36}$ and 5.7 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}36}$ ${\mathrm{cm}}^{2}$/sr with 2- and 3-GeV protons, respectively.