Limiting SUSY-QCD spectrum and its application for decays of superheavy particles

The supersymmetric generalization of the limiting and Gaussian QCD spectra is obtained. These spectra are valid for $x \ll 1$, when the main contribution to the parton cascade is given by gluons and gluinos. The derived spectra are applied to decaying superheavy particles with masses up to the GUT scale. These particles can be relics from the Big Bang or produced by topological defects and could give rise to the observed ultrahigh energy cosmic rays. General formulae for the fluxes of protons, photons and neutrinos due to decays of superheavy particles are obtained.