Nature of Cosmic Rays Underground

The suggestion by Callan and Glashow that there is a new component of cosmic rays comprising stable massive charged particles is examined with respect to present experimental evidence. Direct analysis of particle masses at sea level, the angular distribution of low-energy muons, and the energies of energetic muons at great depths underground all point to the likely nonexistence of these particles, at least to the suggested extent of 10^-3 of the normal primary component.