Super GZK'' Particles in a Classic Kramers' Diffusion-over-a-Barrier Model.

ORAL

Abstract

We present calculated effects of the dispersion in energy loss in photo-pion reactions on the evolution of ultra-high energy cosmic rays (UHECR) protons' energy spectrum. Based on a Fokker-Planck transport equation in energy space, whose transport coefficients are calculated using laboratory measurements, and a derived Fokker-Planck potential, our results show that dispersion in energy loss has significant effects in estimating the protons' horizon distance as well as their energy spectrum. In particular, the Greisen-Zatsepin -Kuzmin horizon in this formalism is estimated to be less than 80 Mpc.In addition, we demonstrate how a Fokker-Planck-potential formalism can distinguish between protons and heavy ions in observed UHECR.

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Authors

  • Samer Alnussirat

    Louisiana State University, Baton Rouge LA 70803, USA

  • Nasser Barghouty

    NASA HQ, Mail Code 7Z58, Quantum Science Program, HEOMD, Washington DC 20546, USA

  • Gary Webb

    Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35805, USA

  • Peter Biermann

    MPI for Radioastronomy, Bonn, Germany