Geant4-Based Characterization of Muon, Electron, Photon, and Hadron Signals from Atmospheric Showers in a Water Cherenkov Detector

Cherenkov radiation is a widely used detection method in high-energy physics experiments, particularly in water-based detectors deployed by leading cosmic-ray observatories. Its popularity arises from its robustness in diverse environments, cost-effectiveness, and high detection efficiency. In this study, we present a detailed Monte Carlo characterization of a Water Cherenkov Detector (WCD) using the Geant4 simulation toolkit. The detector is designed to register secondary particles produced by the interaction of high-energy cosmic-ray protons with Earth’s atmosphere, which generate extensive air showers composed of hadronic, electromagnetic, and muonic components capable of reaching ground level. By modeling the differential energy spectra and angular distributions of these particles at the surface, we evaluate the WCD response in terms of energy deposition, Cherenkov photon production in water, photoelectron generation at the photomultiplier tube, and the resulting charge spectra. The results provide new insights into the detector’s performance and its ability to measure the flux of secondary cosmic rays.