Simulation of extensive air showers and its detection

• Autor(a) principal: Arbeletche, Luan Bonneau
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/76/76134/tde-03092021-115317/
• topic: Chuveiros atmosféricos extensos; Cosmic rays; Extensive air showers; Raios cósmicos; Raios gamma de altas energias; Very-high-energy gamma rays

Ground-based observatories allow for the detection of the most energetic forms of cosmic radiation in a multi-messenger context, including cosmic rays with energies above 1015 eV and gamma rays with energies above 1010 eV. Current experiments, such as the Pierre Auger Observatory, and forthcoming ones, such as the Cherenkov Telescope Array (CTA), have to deal with interpreting extensive air showers to reconstruct the fluxes of particles arriving at Earth. In this scenario, the general purpose of this thesis is to contribute to the improvement of the techniques used to reconstruct the properties of the primary particle in measurements of extensive air showers. In particular, four individual studies based on the simulation of air showers are presented. First, a study of the fluctuations in the atmospheric depth at which a shower reaches its maximum (Xmax) is performed. The best functional form to describe the simulated Xmax distributions is selected and, along with two alternative functions, parametrized. This study aims to improve the reconstruction of the relative abundances of primary masses in the ultra-high-energy regime (E0 > 1017 eV) and to provide a practical tool for any other studies depending on Xmax distributions. Second, the angular distribution of Cherenkov light emitted from extensive air showers is parametrized using simulations performed in a broad energy range: from 100 GeV to 1 EeV. For this, a functional form to describe the angular distribution of Cherenkov photons is built using analytical arguments, and its parameters are constrained to describe the simulated showers. The resulting parametrization can be used to reconstruct the properties of air showers both through fluorescence detectors and Imaging Atmospheric Cherenkov Telescopes (IACT). Third, a technique to measure Xmax through IACTs is developed. The proposed technique is shown to provide a resolution comparable to that of fluorescence detectors, allowing for mass composition studies around the knee in the cosmic-ray spectrum. Fourth, the problem of modeling hadronic interactions is visited in the context of the CTA observatory. An analysis based on simulations is performed to determine the extent to which image parameters reconstructed by IACTs are influenced by uncertainties in hadronic interaction models. Then, a computation of the uncertainty on the estimated CTA sensitivity curve due to hadronic interaction models is performed.