Search for heavy singly charged particles in cosmic rays

A search is being conducted for heavy singly charged particles which might be found in cosmic rays deep in the atmosphere. The search is particularly motivated by the possible existence of particles which might form fundamental triplet representations of SU3. It has been possible to show that such particles will likely have velocities smaller than c near sea level if their angle of incidence is near 15° from the horizontal. The particles are identified by their momentum, charge, and time of flight through the apparatus. No such particles have been found, and the preliminary data give a limit of 2.8 × 10−8 cm−2 sr−1 s−1 at 90% significance level for particles with masses greater than 5 GeV/c2 with a velocity between 0.5c and 0.75c. On the basis of a particular model of production and diffusion through the atmosphere this flux corresponds to a production cross section by nucleon–nucleon interactions of about 10−29 cm2.