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Ultra-high energy cosmic rays may come from clustered sources

John N. Bahcall, Eli Waxman

hep-pharXiv:hep-ph/9912326

Abstract

Clustering of cosmic-ray sources affects the flux observed beyond the cutoff imposed by the cosmic microwave background and may be important in interpreting the AGASA, Fly's Eye, and HiRes data. The standard deviation, sigma, in the predicted number, N, of events above 1020 eV is sigma/N = 0.9(r0/10 Mpc)0.9, where r0 is the unknown scale length of the correlation function (r0 = 10 Mpc for field galaxies). Future experiments will allow the determination of r0 through the detection of anisotropies in arrival directions of ~ 1020 eV cosmic-rays over angular scales of Theta ~ r0/30 Mpc.

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