2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/12363It is proposed that the highest energy $\sim 10^{20}$eV cosmic ray primaries are protons, decay products of a long-lived progenitor whose high kinetic energy arises from decay of a distant (cosmological) superheavy particle, G. Such a scenario can occur in e.g. SU(15) grand unification and in some preon models, but is more generic; if true, these unusual cosmic rays provide a window into new physics.6 pages. LaTeX. Talk at PASCOS-98, Northeastern UniversityAstrophysicstext