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Constraining the cosmic ray source spectrum from observations in the GZK regime

M. Kachelriess E. Parizot 1 D.V. Semikoz 2 
1 APC - AHE - APC - Astrophysique des Hautes Energies
APC (UMR_7164) - AstroParticule et Cosmologie, Dipartimento di Astronomia, Universita degli Studi di Bologna
APC (UMR_7164) - AstroParticule et Cosmologie, Institut für theoretische Physik
Abstract : We discuss the GZK horizon of protons and present a method to constrain the injection spectrum of ultrahigh energy cosmic rays (UHECRs) from supposedly identified extragalactic sources. This method can be applied even when only one or two events per source are observed and is based on the analysis of the probability for a given source to populate different energy bins, depending on the actual cosmic ray injection spectral index. In particular, we show that for a typical source density of 4 × 10−5 Mpc−3, a data set of 100 events above 6 × 1019 eV allows one in 97% of all cases to distinguish a source spectrum dN/dE ∝ E −1.1 from one with E -2.7 at 95% confidence level.
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Submitted on : Monday, January 7, 2008 - 2:42:21 PM
Last modification on : Thursday, November 18, 2021 - 3:58:05 AM

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M. Kachelriess, E. Parizot, D.V. Semikoz. Constraining the cosmic ray source spectrum from observations in the GZK regime. JETP Letters, Springer Verlag, 2008, 88, pp.553-557. ⟨10.1134/S0021364008210017⟩. ⟨in2p3-00202602⟩



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