ULTRAHIGH-ENERGY COSMIC-RAYS, SUPERHEAVY LONG-LIVED PARTICLES, AND MATTER CREATION AFTER INFLATION

Cosmic rays of the highest energy, above the Greisen-Zatsepin-Kuzmin ( GZK) cutoff of the spectrum, may originate in decays of superheavy lon g-lived particles. We conjecture that these particles may be produced naturally in the early Universe from vacuum fluctuations during inflat ion and may constitute a considerable fraction of cold dark matter. We predict a new cutoff in the ultrahigh-energy cosmic ray spectrum E-cu toff < m(inflaton) approximate to 10(13) GeV, the exact position of th e cutoff and the shape of the cosmic ray spectrum beyond the GZK cutof f being determined by the QCD quark/gluon fragmentation. The Pierre Au ger Project installation may in principle observe this phenomenon. (C) 1998 American Institute of Physics. [S0021-3640(98)00116-9].