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This content will become publicly available on September 22, 2018

Title: Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 × 10 18 eV

We report that cosmic rays are atomic nuclei arriving from outer space that reach the highest energies observed in nature. Clues to their origin come from studying the distribution of their arrival directions. Using $$3 \times 10^4$$ cosmic rays above $$8 \times 10^{18}$$ electron volts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 square kilometers steradian year, we report an anisotropy in the arrival directions. The anisotropy, detected at more than the 5.2$$\sigma$$ level of significance, can be described by a dipole with an amplitude of $$6.5_{-0.9}^{+1.3}$$% towards right ascension $$\alpha_{d} = 100 \pm 10$$ degrees and declination $$\delta_{d} = -24_{-13}^{+12}$$ degrees. Lastly, that direction indicates an extragalactic origin for these ultra-high energy particles.
Authors:
;
Publication Date:
Report Number(s):
FERMILAB-PUB-17-354; arXiv:1709.07321
Journal ID: ISSN 0036-8075; 1624662
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
Science
Additional Journal Information:
Journal Volume: 357; Journal Issue: 6357; Journal ID: ISSN 0036-8075
Publisher:
AAAS
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
The Pierre Auger Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS
OSTI Identifier:
1395473