Cosmic Rays: The Second Knee and Beyond

Abstract

We conduct a review of experimental results on Ultra-High Energy Cosmic Rays (UHECR's) including measurements of the features of the spectrum, the composition of the primary particle flux and the search for anisotropy in event arrival direction. We find that while there is a general consensus on the features in the spectrum -- the Second Knee, the Ankle, and (to a lesser extent) the GZK Cutoff -- there is little consensus on the composition of the primaries that accompany these features. This lack of consensus on the composition makes interpretation of the agreed upon features problematic. There is also little direct evidence about potential sources of UHECRs, as early reports of arrival direction anisotropies have not been confirmed in independent measurements.

46 pages, 30 figures. Topical Review to appear in J. Physics G

References in corpus (2)

• New facts about muon production in Extended Air Shower simulations
• Observation of the GZK Cutoff Using the HiRes Detector

Cited by in corpus (6)

• Cosmic Rays from the Knee to the Highest Energies
• Review of the Safety of LHC Collisions
• Planck-scale Lorentz violation constrained by Ultra-High-Energy Cosmic Rays
• Air Fluorescence Relevant for Cosmic-Ray Detection - Summary of the 5th Fluorescence Workshop, El Escorial 2007
• Signatures of the transition from galactic to extragalactic cosmic rays
• Foundations of anisotropic relativistic mechanics