The physics of ultra-high-energy cosmic rays in the context of the Pierre Auger Observatory: Main results and future perspectives

For almost 20 years, the Pierre Auger Observatory has studied ultrahigh-energy cosmic rays (UHECRs) using its unique hybrid design, which employs a ground array of water-Cherenkov detectors along with 27 fluorescence telescopes to observe extensive air showers with different, complementary techniques. Some fundamental results include measurements of the energy spectrum, of the primary mass composition and of the arrival directions with unprecedented accuracy. Although no specific source has been pinpointed yet, these findings have significantly improved our understanding of UHECR and set the stage for the upgrade of the experimental setup, called AugerPrime, currently under finalization.