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

Authors

J. Abraham, Universidad Tecnolo´gica Nacional, FR-Mendoza, Argentina
Gregory Snow, University of Nebraska - LincolnFollow
The Pierre Auger Collaboration

Date of this Version

August 2008

Comments

Published in PRL 101, 061101 (2008). Copyright 2008. Used by permission.

Abstract

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 γ of the particle flux, J/ E^{- γ} , 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.