Limits on Charmed-Particle Production in Proton-Nucleus Collisions at 400 GeV/c

We have searched for the charmed and other new particles by measuring the hadron pair mass spectra in proton-nucleus collisions at 400 GeV/c. Results are presented for ${\pi }^{-}{K}^{+}$, ${\pi }^{+}{K}^{-}$, and ${\pi }^{+}{\pi }^{-}$ pairs in the mass region from 1.5 to 4.0 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$. No evidence for narrow resonances was found. The sensitivity of the search varied from 2 × ${10}^{-30\mathrm{}}$ ${\mathrm{cm}}^2$ at 2 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$ to 5 × ${10}^{-32\mathrm{}}$ ${\mathrm{cm}}^2$ at 4 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^2$. Experimental checks were provided by the observation of a clean $\frac{J}{\psi \mathrm{}\left(3.1\right)\mathrm{}}\to {\mu }^{+}{\mu }^{-}$ signal.