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 long-lived particles. We conjecture that these particles may be produced naturally in the early Universe from vacuum fluctuations during inflation and may constitute a considerable fraction of cold dark matter. We predict a new cutoff in the ultrahigh-energy cosmic ray spectrum E cutoff<m inflaton≈1013 GeV, the exact position of the cutoff and the shape of the cosmic ray spectrum beyond the GZK cutoff being determined by the QCD quark/gluon fragmentation. The Pierre Auger Project installation may in principle observe this phenomenon.