Evidence Against the Mass-500 Particle

Abstract

The existence of a mass-500 particle was investigated by exposing a nuclear emulsion to cosmic rays at an altitude of 10 600 feet and geomagnetic latitude 39°. Particles of average range, 60 g/${\mathrm{cm}}^2$ of copper, were stopped in the emulsion and grain counted at a residual range of 1 cm. The available track length was such that the existence of a mass-500 particle would have been established on the basis of a single occurrence. About 1100 muons were found with no particles in the region of 500 electron masses being observed. This is not consistent with the abundance reported by Alikhanian et al., since the probability of finding none, assuming their reported abundance, is 0.4%.