Ultra - High Energy Cosmic Rays , Superheavy Long - Living Particles , and Matter Creation after Inflation

The highest energy cosmic rays, above the Greisen–Zatsepin–Kuzmin cut-off of cosmic ray spectrum, may be produced in decays of superheavy long-living X-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 cut-off in the UHE cosmic ray spectrum Ecut−off < minflaton ≈ 10 GeV, the exact position of the cut-off and the shape of the cosmic ray spectrum beyond the GZK cut-off being determined by the QCD quark/gluon fragmentation. The Pierre Auger Project installation might discover this phenomenon. PACS numbers: 98.70.Sa, 95.35.+d, 98.80.Cq Typeset using REVTEX email address: [email protected] email address: [email protected]