Gamma/Hadron Separation Method for the HADAR Experiment

Abstract

Ground-based arrays of imaging atmospheric Cherenkov telescopes (IACTs) are the most sensitive γ-ray detectors for energies of approximately 100 GeV and above. One such IACT is the High Altitude Detection of Astronomical Radiation (HADAR) experiment,
which uses a large aperture refractive water lens system to capture atmospheric Cherenkov photons (i.e., the imaging atmospheric Cherenkov technique). The telescope array has a low threshold energy and large field of view, and can continuously scan the area of the sky being observed, which is conducive to monitoring and promptly responding to transient phenomena. The process of γ-hadron separation is essential in very-high-energy (VHE; >30 GeV) γ-ray astronomy and is a key factor for the successful utilization of IACTs. In this study, Monte Carlo (MC) simulations were carried out to model the response of cosmic rays within the HADAR detectors. By analyzing the Hillas parameters and the distance between the event core and the telescope, the distinction between air showers initiated by γ rays and those initiated by cosmic rays was determined. Additionally, a Quality Factor was introduced to assess the telescope’s ability to suppress the background and to provide a more effective characterization of its performance.