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arXiv · 1802.05003

Evidence of Intermediate-Scale Energy Spectrum Anisotropy of Cosmic Rays E$\geq$10$^{19.2}$ 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. Hanlon·M. 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. M. 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·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·S. 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
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Abstract

An intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays of energies above $10^{19.2}$ eV in the northern hemisphere, using 7 years of data from the Telescope Array surface detector. 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 $9^h$$16^m$, $45^{\circ}$. and has a deficit of events with energies $10^{19.2}$$\leq$$E$$<$$10^{19.75}$ eV and an excess for $E$$\geq$$10^{19.75}$ eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be $9$$\times$$10^{-5}$ ($3.74$$\sigma_{global}$).

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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. Hanlon, M. 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. M. 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, 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, S. 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. 2018-02-14. Evidence of Intermediate-Scale Energy Spectrum Anisotropy of Cosmic Rays E$\geq$10$^{19.2}$ eV with the Telescope Array Surface Detector. https://doi.org/10.3847/1538-4357/aac9c8

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