Contributions of cosmic-ray components to the HPGe gamma spectrometer background spectrum within the 0°-45° Zenith angle range

This study investigates the contributions of various cosmic-ray-induced components to the energy response of a High-Purity Germanium (HPGe) gamma spectrometer within the 0 degrees-45 degrees zenith angle range. The analysis focuses on muons, neutrons, protons, electrons, positrons, and photons. It also examines the impact of particle showers induced by muons interacting with the lead chamber and reaching the HPGe detector. Utilizing the GEANT4 simulation toolkit, we provide a detailed examination of these components' influence on the spectrum. The results confirm that within this zenith angle range, muons account for approximately 91% of the recorded cosmic-ray induced energy spectrum and contribute 54.6% to the overall cosmic-ray-induced background spectrum. The study also highlights the significant role of showers, especially those resulting from muon interactions with the lead shielding, in shaping the low-energy spectrum below 3 MeV.