Recent results from the Pierre Auger Observatory

Abstract

The main results from the Auger Observatory are described. A steepening of the spectrum is observed at the highest energies, supporting the expectation that above $4\times 10^{19}$ eV the cosmic ray energies are significantly degraded by interactions with the CMB photons (the GZK effect). This is further supported by the correlations observed above $6\times 10^{19}$ eV with the distribution of nearby active galaxies, which also show the potential of Auger to start the era of charged particle astronomy. The lack of observation of photons or neutrinos strongly disfavors top-down models, and these searches may approach in the long term the sensitivity required to test the fluxes expected from the secondaries of the very same GZK process. Bounds on the anisotropies at EeV energies contradict hints from previous experiments that suggested a large excess from regions near the Galactic centre or the presence of a dipolar type modulation of the cosmic ray flux.