Observation of the suppression of the flux of cosmic rays above 4x10(19) eV


The 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 to E-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.

UPPER LIMIT, ENERGY, AIR, SHOWERS, ARRAY, Physics, Multidisciplinary, Physics
Abraham, J., et al. (2008): Observation of the Suppression of the Flux of Cosmic Rays above 4 × 1019 eV. Physical Review Letters, 101(6). DOI: http://dx.doi.org/10.1103/PhysRevLett.101.061101