Testing astrophysical models to understand the features in the cosmic rays spectrum.
Condorelli A., Boncioli D., Petrera S., Salamida F.
III - Astrofisica
Aula GSSI Ex ISEF - Biblioteca - Venerdì 27 h 15:30 - 19:00
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The aim of Pierre Auger Observatory, the largest experiment detecting Ultra High Energy Cosmic Rays (UHECRs), is to measure the cosmic rays at the highest energies with unprecedented precision. A change in the spectral index of the cosmic ray spectrum at about 5 EeV has been observed, which is called ankle, and the suppression at the highest energies has been measured with high significance. In addition, Auger provides a robust measurement of the mass composition of the UHECRs, which evolves towards a lighter composition at lower energies, while at higher energies the trend is reversed. Several investigations have been done for testing possible model UHECRs sources, in particular a combined fit to both the energy spectrum and mass composition has been provided. What concerns most our studies is to infer something about the astrophysical scenario that could reproduce the Pierre Auger data. Several investigations have been done in the recent years to interpret the UHECR spectrum and composition, finding scenarios with sources injecting hard spectra with low rigidity cutoff and mixed composition, even though simplifying assumptions are used as uniform source distributions and 1D cosmic-ray propagation. We are currently working not just on the propagation of these particles but, in particular, on a more sophisticated source model in order to improve the physical understanding of the features in the cosmic-rays data across the ankle.