Hints on the Existence of Superheavy Dark matter and Ultrahigh Energy Dark Matter in Extreme Energy Cosmic Rays Observations

Abstract

In the present paper, it is assumed that there exist two dark matter particles: superheavy dark matter particles (SHDM), whose mass $\sim$ inflaton mass, and lighter fermion dark matter particles (LFDM) which are the ultra-relativistic products of its decay. The event rates of LFDM measured by the Pierre Auger observatory (Auger) are evaluated in the energy range between 1 EeV and 1 ZeV at the zenith angles between 0$^{\circ}$ and 60$^{\circ}$ when the different lifetimes of decay of SHDM. Thus it is proved that the possibility of measurement of these LFDM at Auger. Based on the assumption that the detection efficiency for a shower caused by LFDM is set to be 100\%, the LFDM contribution to the energy spectrum of extreme energy cosmic rays (EECRs) is discussed. And it is found that there are some hints on the existence of SHDM and LFDM in the past EECRs observations.