Speaker
Description
We report a measurement of the ultra-high-energy cosmic-ray spectrum based on the full Phase I data set of the Pierre Auger Observatory, corresponding to data collected from 2004 to 2022. The analysis combines the spectra independently reconstructed from two independent event sets from the surface array above 2.5 EeV, using a forward-folding approach to account for detector effects and to derive a consistent spectrum over the full field of view of the Observatory. With an exposure of about 104900 km$^2$sr$~$yr, this data set provides the most complete Auger determination of the energy spectrum in the Phase I era. The measurement confirms the ankle, the instep around 10 EeV, and the suppression at the highest energies with increased significance and precision. The spectrum is also studied in different declination intervals, and no significant dependence on declination is found within the present statistics beyond the modulation expected from the established large-scale dipolar anisotropy. These results provide an important reference for astrophysical interpretations of the spectral features and for future comparisons with the upcoming Phase II measurements.