Search for long-lived exotic particles in 12-GeV proton-nucleus interactions

A sensitive search for the production of exotic hadrons with charge z=±2 and z=-(5/3 has been carried out with a 12-GeV proton beam. No candidate event was found in the mass range up to M/z=1.2 GeV/$c^2$. Upper limits are established at ∼${10}^{\mathrm{-}9}$ on the yield of such particles relative to the π yield. In particular, this experiment has ruled out the existence of R-${\Delta }^{++}$’s with a mass of less than ∼1.6 GeV/$c^2$ and a lifetime longer than ∼${10}^{\mathrm{-}7}$ sec.