Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection (GRAND) is a proposed large-scale observatory designed to detect cosmic rays, gamma-rays, and neutrinos with energies exceeding 100 PeV. The GRANDProto300 experiment is proposed as the early stage of the GRAND project, consisting of a hybrid array of radio antennas and scintillator detectors. The latter, as a mature and traditional detector, is used to cross-check the nature of the candidate events selected from radio observations. In this study, we developed a simulation software called G4GRANDProto300, based on the Geant4 software package, to optimize the spacing of the scintillator detector array and to investigate its effective area. The analysis was conducted at various zenith angles under different detector spacings, including 300, 500, 600, 700, and 900 m. Our results indicate that, for large zenith angles used to search for cosmic-ray in the GRAND project, the optimized effective area is with a detector spacing of 500 m. The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.