Astrophysical origins of ultrahigh energy cosmic rays

Abstract

In the first part of this review we discuss the basic observational features\nat the end of the cosmic ray energy spectrum. We also present there the main\ncharacteristics of each of the experiments involved in the detection of these\nparticles. We then briefly discuss the status of the chemical composition and\nthe distribution of arrival directions of cosmic rays. After that, we examine\nthe energy losses during propagation, introducing the Greisen-Zaptsepin-Kuzmin\n(GZK) cutoff, and discuss the level of confidence with which each experiment\nhave detected particles beyond the GZK energy limit. In the second part of the\nreview, we discuss astrophysical environments able to accelerate particles up\nto such high energies, including active galactic nuclei, large scale galactic\nwind termination shocks, relativistic jets and hot-spots of Fanaroff-Riley\nradiogalaxies, pulsars, magnetars, quasar remnants, starbursts, colliding\ngalaxies, and gamma ray burst fireballs. In the third part of the review we\nprovide a brief summary of scenarios which try to explain the super-GZK events\nwith the help of new physics beyond the standard model. In the last section, we\ngive an overview on neutrino telescopes and existing limits on the energy\nspectrum and discuss some of the prospects for a new (multi-particle)\nastronomy. Finally, we outline how extraterrestrial neutrino fluxes can be used\nto probe new physics beyond the electroweak scale.\n