Features of the Energy Spectrum of Cosmic Rays above 2.5 × 10 18 eV Using the Pierre Auger Observatory

We report a measurement of the energy spectrum of cosmic rays above 2.5×1018 eV based on 215 030 events. New results are presented: at about 1.3×1019eV, the spectral index changes from 2.51±0.03(stat)±0.05(syst) to 3.05±0.05 (stat) ±0.10 (syst), evolving to 5.1±0.3 (stat) ±0.1 (syst) beyond 5×1019e, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. .