On Spectrum of Extremely High Energy Cosmic Rays through Decay of Superheavy Particles

We propose a formula for flux of extremely high energy cosmic rays (EHECR) through decay of superheavy particles. It is shown that EHECR spectrum reported by AGASA is reproduced by the formula. The presence of EHECR suggests, according to this approach, the existence of superheavy particles with mass of about $7\times {10}^{11}$GeV and the lifetime of about ${10}^9$ years. Possibility to obtain a knowledge of ${\mathrm{\Omega }}_0$ of the universe from the spectrum of EHECR is also pointed out.