INVESTIGATING THE ORIGINS OF UHECRS USING THE PIERRE AUGER OBSERVATORY AND PALEO-DETECTORS

A very fascinating region for investigating the origins of cosmic rays is the toe of the ultra-high energy cosmic ray (UHECR) spectrum, above ≈ 50 EeV. The potential for small magnetic deflections at these energies is coupled with the presence of flux suppression, which may be a sign of the sources’ maximum acceleration potential or may have an explanation for the interactions of cosmic rays with background photons, effectively restricting the region of interest in the search for UHECR sources to a relatively small bubble around us. In this thesis, I present the latest dataset of cosmic rays at the highest energies collected by the Pierre Auger Observatory, the largest experiment dedicated to UHECR science ever built, and the anisotropy searches carried out using it. I have carried out blind, model-independent searches for overdensities, astrophysical structural correlation analysis, and cross-correlation investigations with catalogs of candidate sources. For UHECRs with energy greater than 38 EeV, the results show evidence of a deviation from isotropy at an angular scale of ≈ 25◦ at the 4σ level. Additionally in this thesis for the first time, I present the possibility of using ancient minerals as paleo-detectors to study the history of the flux of cosmic rays in the past by detecting the tracks left in the mineral structure by the interactions between ions and energetic secondary cosmic rays present in the extensive airshowers.