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Type: Journal article
Title: Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
Author: Barber, K.
Bellido Caceres, J.
Clay, R.
Cooper, M.
Dawson, B.
Herve, A.
Holmes, V.
Sorokin, J.
Wahrlich, P.
Whelan, B.
Winnick, M.
Citation: Journal of Cosmology and Astroparticle Physics, 2011; 2011(6):1-16
Publisher: Institute of Physics Publishing Ltd
Issue Date: 2011
ISSN: 1475-7516
Statement of
K.B. Barber... J.A. Bellido... R.W. Clay... M.J. Cooper... B.R. Dawson... A.E. Herve... V.C. Holmes... J. Sorokin... P. Wahrlich... B.J. Whelan... M.G. Winnick... et al., for The Pierre Auger Collaboration
Abstract: The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5 × 1019 eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrative values of Z = 6,13,26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.
Keywords: ultra high energy cosmic rays
cosmic ray experiments
Rights: © 2011 IOP Publishing Ltd and SISSA
DOI: 10.1088/1475-7516/2011/06/022
Grant ID: ARC
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