Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays e ≥ 1019.2 eV with the Telescope Array Surface Detector

R. U. Abbasi, M. Abe, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, R. Cady, B. G. Cheon, J. Chiba, M. Chikawa, A. Di Matteo, T. Fujii, K. Fujita, M. Fukushima, G. Furlich, T. Goto, W. HanlonM. Hayashi, Y. Hayashi, N. Hayashida, K. Hibino, K. Honda, D. Ikeda, N. Inoue, T. Ishii, R. Ishimori, H. Ito, D. Ivanov, H. M. Jeong, S. Jeong, C. C.H. Jui, K. Kadota, F. Kakimoto, O. Kalashev, K. Kasahara, H. Kawai, S. Kawakami, S. Kawana, K. Kawata, E. Kido, H. B. Kim, J. H. Kim, J. H. Kim, S. Kishigami, S. Kitamura, Y. Kitamura, V. Kuzmin, M. Kuznetsov, Y. J. Kwon, K. H. Lee, B. Lubsandorzhiev, J. P. Lundquist, K. Machida, K. Martens, T. Matsuyama, J. N. Matthews, R. Mayta, M. Minamino, K. Mukai, I. Myers, K. Nagasawa, S. Nagataki, R. Nakamura, T. Nakamura, T. Nonaka, A. Nozato, H. Oda, S. Ogio, J. Ogura, M. Ohnishi, H. Ohoka, T. Okuda, Y. Omura, M. Ono, R. Onogi, A. Oshima, Shunsuke Ozawa, I. H. Park, M. S. Pshirkov, D. C. Rodriguez, G. Rubtsov, D. Ryu, H. Sagawa, R. Sahara, K. Saito, Y. Saito, N. Sakaki, N. Sakurai, L. M. Scott, T. Seki, K. Sekino, P. D. Shah, F. Shibata, T. Shibata, H. Shimodaira, B. K. Shin, H. S. Shin, J. D. Smith, P. Sokolsky, B. T. Stokes, S. R. Stratton, T. A. Stroman, T. Suzawa, Y. Takagi, Y. Takahashi, M. Takamura, R. Takeishi, A. Taketa, M. Takita, Y. Tameda, H. Tanaka, K. Tanaka, M. Tanaka, S. B. Thomas, G. B. Thomson, P. Tinyakov, I. Tkachev, H. Tokuno, T. Tomida, S. Troitsky, Y. Tsunesada, K. Tsutsumi, Y. Uchihori, S. Udo, F. Urban, T. Wong, M. Yamamoto, R. Yamane, H. Yamaoka, K. Yamazaki, J. Yang, K. Yashiro, Y. Yoneda, S. Yoshida, H. Yoshii, Y. Zhezher, Z. Zundel

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12 Citations (Scopus)

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 1019.2 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 1019.2 ≤ E < 1019.75 eV and an excess for E ≥ 1019.75 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).

Original languageEnglish
Article number91
JournalAstrophysical Journal
Volume862
Issue number2
DOIs
Publication statusPublished - 2018 Aug 1

Keywords

  • astroparticle physics
  • cosmic rays
  • large-scale structure of universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Abbasi, R. U., Abe, M., Abu-Zayyad, T., Allen, M., Azuma, R., Barcikowski, E., Belz, J. W., Bergman, D. R., Blake, S. A., Cady, R., Cheon, B. G., Chiba, J., Chikawa, M., Matteo, A. D., Fujii, T., Fujita, K., Fukushima, M., Furlich, G., Goto, T., ... Zundel, Z. (2018). Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays e ≥ 1019.2 eV with the Telescope Array Surface Detector. Astrophysical Journal, 862(2), [91]. https://doi.org/10.3847/1538-4357/aac9c8