Análise da composição dos raios cósmicos de ultra energéticos e sua relação com a radiação de fundo

Abstract

This work investigates the effects of extragalactic background light (EBL), cosmic radio background (CRB/URB), and propagation distance on the depth of maximum development (Ĕmax) of extensive air showers induced by ultra-high-energy cosmic rays (UHECRs). Using numerical simulations based on the CRPropa 3 code, a large set of particles was propagated from their emission at the source to their interaction with the Earth’s atmosphere, considering different primary compositions and updated physical models. Variations in the energy spectrum and Ĕmax were analyzed by comparing different propagation scenarios. The results indicate that the choice of the EBL model significantly affects Ĕmax, with variations of up to 2.6% between extreme models, with the most pronounced effects for heavy nuclei such as iron and nitrogen. Additionally, propagation distance directly influences the maximum depth, with differences reaching 3.1% for distances exceeding 500 Mpc, demonstrating that accumulated interactions along the trajectory modify the composition of UHECRs. The inclusion of CRB showed a secondary effect, with a maximum impact of 0.7% on Ĕmax, being more relevant for heavy nuclei due to enhanced photodisintegration processes. Comparison with experimental data from the Pierre Auger Observatory reinforces the importance of these interactions in reconstructing the primary composition of UHECRs and calibrating propagation models. The findings of this study contribute to a better understanding of the influence of cosmological factors on the evolution of ultra-high-energy cosmic rays, aiding in the refinement of theoretical models applied to particle astrophysics.