Ultrahigh Energy Cosmic Rays: Review of the Current Situation

Abstract

We describe the current situation of the data on the highest energy particles in the Universe -the ultrahigh energy cosmic rays. The new results in the field come from the Telescope Array experiment in Utah, U.S.A. For this reason we concentrate on the results from this experiments and compare them to the measurements of the other two recent experiments, the High Resolution Fly's Eye and the Southern Auger Observatory.Keywords: High energy cosmic rays -Hadronic interaction at very high energy -Origin of the highest energy cosmic rays.

Mass composition studies of Ultra High Energy cosmic rays through the measurement of the Muon Production Depths at the Pierre Auger Observatory

“…energy at which the flux has lowered to half of its value, is E 1/2 = 4 • 10 19 eV as measured by Auger, with a spectral index above it of 4.2 ± 0.1. The same feature, although at a higher energies, E 1/2 = 5.6 • 10 19 eV, has been observed by HiRes and TA [Stanev (2012)]. The statistical significance of the cut-off is more than 5σ.…”

“…The Auger Figure 1.2: The cosmic ray spectrum for the highest energy region, as measured by HiRes, Auger and TA. The particle flux is multiplied by E 3 to show better the shape of the energy spectrum [Stanev (2012)] spectrum has a slightly different shape. From 4 • 10 18 eV to 4 • 10 19 eV the slope of the spectrum is 2.68 ± 0.01.…”

“…The six areas defined within the Auger field of view have equal exposures. The events that form a pair at angular distance less than 5 • are circled[Stanev (2012)].…”