R. U. Abbasi (Author), Mitsuhiro Abe (Author), T. Abu-Zayyad (Author), M. Allen (Author), R. Anderson (Author), R. Azuma (Author), E. Barcikowski (Author), J. W. Belz (Author), D. R. Bergman (Author), S. A. Blake (Author), J. P. Lundquist (Author)

Abstract

Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 10^19.2 eV in the northern hemisphere using 7 years of Telescope Array surface detector data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 9h16m, 45°, and has a deficit of events with energies 10^19.2 ≤ E < 10^19.75 eV and an excess for E ≥ 10^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74σ global).

Keywords

cosmic rays;astroparticle physics;anisotropy;large-scale structure;universe;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UNG - University of Nova Gorica
UDC: 524
COBISS: 5616379 Link will open in a new window
ISSN: 1538-4357
Views: 2341
Downloads: 182
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Other data

URN: URN:SI:UNG
Type (COBISS): Not categorized
Pages: str. 1-6
Volume: ǂVol. ǂ862
Issue: ǂno. ǂ2
Chronology: 2018
DOI: 10.3847/1538-4357/aac9c8
ID: 11578982