Search For Long-Lived Heavy Particles

We have performed a high-sensitivity search for massive long-lived particles produced at 2.5 mrad by 400-GeV/c protons on a beryllium target using time-of-flight, Cherenkov, and calorimetric techniques. A total of ${10}^{11}$ light particles (${\ensuremath{\pi}}^{\ensuremath{-}},{K}^{\ensuremath{-}},\overline{p}$) was sampled at 70 GeV/c. This experiment places a limit of 1.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}37}$ ${\mathrm{cm}}^{2}$/${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$ \ifmmode\cdot\else\textperiodcentered\fi{} nucleon on the invariant cross section for the production of stable particles in the mass range of 4 to 10 ${\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$.