Observation of the Suppression of the Flux of Cosmic Rays above 4 x 1019 eV

THE PIERRE AUGER COLLABORATION (INCLUIDO D, MELO); D. MELO

Physical Review Letters

American Physical Society

Año: 2008 vol. 101 p. 61101 - 61107

The energy spectrum of cosmic rays above 2.5 x 1018 eV, derived from 20 000 events recorded at the Pierre Auger Observatory, is described. The spectral index g of the particle flux, J µ E-g, at energies between 4 x 1018 eV and 4 x 1019 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.