Observation of the Suppression of the Flux of Cosmic Rays above 4 x 10^19 eV

THE PIERRE AUGER COLLABORATION (J. ABRAHAM, ..., A.D. SUPANITSKY, ...)

PHYSICAL REVIEW LETTERS

The American Physical Society

Año: 2008 vol. 101 p. 611011 - 611017

0031-9007

The energy spectrum of cosmic rays above 2.5x10^18 eV derived from 20000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J propto E^-gamma, at energies between 4x10^18 eV and 4x10^19 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 Kuzmin.