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Title:Indications of anisotropy at large angular scales in the arrival directions of cosmic rays detected at the Pierre Auger Observatory
Authors:ID Al Samarai, Imen (Author)
ID Filipčič, Andrej (Author)
ID Kukec Mezek, Gašper (Author)
ID Saleh, Ahmed (Author)
ID Stanič, Samo (Author)
ID Trini, Marta (Author)
ID Veberič, Darko (Author)
ID Vorobiov, Serguei (Author)
ID Yang, Lili (Author)
ID Zavrtanik, Danilo (Author)
ID Zavrtanik, Marko (Author), et al.
Files:.pdf ICRC2015_372.pdf (862,90 KB)
MD5: 5A054C1C3958B3C3399A764A63837713
 
Language:English
Work type:Not categorized
Typology:1.08 - Published Scientific Conference Contribution
Organization:UNG - University of Nova Gorica
Abstract:The large-scale distribution of arrival directions of high-energy cosmic rays carries major clues to understanding their origin. The Pierre Auger Collaboration have implemented different analyses to search for dipolar and quadrupolar anisotropies in different energy ranges spanning four orders of magnitude. A common phase ≈270◦ of the first harmonic modulation in right-ascension was found in adjacent energy intervals below 1 EeV, and another common phase ≈100◦ above 4 EeV. A constancy of phase measurements in ordered energy intervals originating from a genuine anisotropy is expected to appear with a smaller number of events than those needed to achieve significant amplitudes. This led us to design a prescribed test aimed at establishing whether this consistency in phases is real at 99% CL. The test required a total independent exposure of 21,000 km2 sr yr. We report on the status of this prescription. We also report the results of the search for a dipole anisotropy for cosmic rays with energies above 4 EeV using events with zenith angles between 60◦ and 80◦. Compared to previous analyses of events with zenith angles smaller than 60◦, this extension increases the size of the data set by 30%, and enlarges the fraction of exposed sky from 71% to 85%. The largest departure from isotropy is found in the energy range above 8 EeV, with an amplitude for the first harmonic in right ascension r1 = (4.4 ± 1.0) × 10[sup]−2, that has a chance probability P(≥ r1) = 6.4×10[sup]−5, reinforcing the hint previously reported with vertical events alone.
Keywords:high-energy cosmic rays large-scale distribution anisotropy studies Pierre Auger Observatory
Publication status:Published
Year of publishing:2015
PID:20.500.12556/RUNG-2133 New window
COBISS.SI-ID:4150523 New window
NUK URN:URN:SI:UNG:REP:IXMK901I
Publication date in RUNG:02.03.2016
Views:5101
Downloads:238
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Record is a part of a monograph

Title:The 34th International Cosmic Ray Conference : ICRC 2015 (The Hague, Netherlands)
Publisher:PoS, http://pos.sissa.it/
Year of publishing:2015
Conference organizer:International Union of Pure and Applied Physics (IUPAP)
Collection title:Proceedings of ICRC 2015

Licences

License:CC BY-NC-SA 4.0, Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International
Link:http://creativecommons.org/licenses/by-nc-sa/4.0/
Description:A Creative Commons license that bans commercial use and requires the user to release any modified works under this license.
Licensing start date:02.03.2016

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