J. AbrahamP. AbreuM. AgliettaC. AguirreD. AllardI. AllekotteJ. AllenP. AllisonJaime Álvarez-MuñizM. Ambrosio2026-03-222026-03-22200810.1103/physrevlett.101.061101https://doi.org/10.1103/physrevlett.101.061101https://andeanlibrary.org/handle/123456789/42997Citaciones: 617The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and by Zatsepin and Kuz'min.lvPierre Auger ObservatoryPhysicsCosmic rayFlux (metallurgy)Spectral indexAstrophysicsAtomic physicsNuclear physicsarticle