TY  - JOUR
AU  - Pierre Auger Collaboration (Abreu, P. et al
AU  - Pastor, S.
PY  - 2011
DA  - 2011//
TI  - Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
T2  - J. Cosmol. Astropart. Phys.
JO  - Journal of Cosmology and Astroparticle Physics
SP  - 022
EP  - 17pp
VL  - 06
IS  - 6
PB  - Iop Publishing Ltd
KW  - ultra high energy cosmic rays
KW  - cosmic ray experiments
AB  - The Pierre Auger Collaboration has reported. evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > E-th = 5.5 x 10(19) 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 > E-th 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 E-th/Z (for illustrative values of Z = 6, 13, 26). If the anisotropies above E-th 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.
SN  - 1475-7516
UR  - http://arxiv.org/abs/1106.3048
UR  - https://doi.org/10.1088/1475-7516/2011/06/022
DO  - 10.1088/1475-7516/2011/06/022
LA  - English
N1  - ISI:000292332400022
ID  - PierreAugerCollaborationAbreu+Pastor2011
ER  -