Energy spectrum of particles arriving at the ground and S(800) determination by Monte Carlo simulation for Telescope Array

Telescope Array (TA) experiment in Utah, USA, observes ultrahigh-energy cosmic rays (UHECRs); UHECRs refer cosmic rays with energy above $10^{18}eV$. Using COSMOS and CORSIKA, we have produced a library of over 1000 thinned extensive air shower (EAS) simulations with the primary energies ranging from $10^{18.5}eV$ to $10^{20.25}eV$ and the zenith angle of primary cosmic ray particle from $0^{\circ}$ to $45^{\circ}$. Here, we present the energy spectrum of particles arriving at the ground. We have also calculated the detector response evaluated using GEANT4 simulations. Here, we discuss S(800), i.e. the signal at a distance of 800 m from the shower core, as the primary energy estimator.