Joint analysis of the energy spectrum of ultra-high-energy cosmic rays as measured at the Pierre Auger Observatory and the Telescope Array
Y. Tsunesada, Telescope Array, Rasha Abbasi, T. Abu‐Zayyad, Monica Allen, Yuto Arai, Ryuhei Arimura, E. Barcikowski, John Belz, D. R. Bergman, Samuel Blake, R. Cady, ByongGu Cheon, Jyunsei Chiba, Michiyuki Chikawa, Toshihiro Fujii, Kozo Fujisue, K. Fujita, Ryota Fujiwara, M. Fukushima, Ryota Fukushima, Greg Furlich, Ricardo González, W. Hanlon, Motoki Hayashi, N. Hayashida, K. Hibino, Ryo Higuchi, Ken Honda, D. Ikeda, Taichi Inadomi, Naoya Inoue, Takaaki Ishii, Hirotaka Ito, D. Ivanov, Hirokazu Iwakura, Aoi Iwasaki, Hyoming Jeong, Soomin Jeong, Charlie Jui, K. Kadota, F. Kakimoto, O. Kalashev, K. Kasahara, Saori Kasami, Hideyuki Kawai, S. Kawakami, S. Kawana, Katsumasa Kawata, Ivan Kharuk, E. Kido, HangBae Kim, Jihee Kim, Jihyun Kim, Min Hyo Kim, Sang‐Woo Kim, Yusuke Kimura, Shoichi Kishigami, Yuto Kubota, Shinnosuke Kurisu, Vladim Kuzmin, M. Kuznetsov, Youngjoon Kwon, Kwang‐Ho Lee, BayarJon Paul Lubsandorzhiev, Jon Paul Lundquist, Kazuhiro Machida, Hiroyuki Matsumiya, Toshio Matsuyama, J. N. Matthews, R. Mayta, M. Minamino, Keijiro Mukai, I. Myers, Shigehiro Nagataki, Kei Nakai, Ryo Nakamura, Toru Nakamura, Tomoyuki Nakamura, Yuya Nakamura, Arata Nakazawa, Eiji Nishio, T. Nonaka, Hiroyuki Oda, S. Ogio, M. Ohnishi, H. Ohoka, Yuya Oku, Takeshi Okuda, Yugo Omura, M. Ono, R. Onogi, A. Oshima, S. Ozawa, Il Hung Park, Matt Potts, М. С. Пширков, Jackson Remington, Doug Rodriguez, Г. И. Рубцов
Abstract
The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin and acceleration mechanisms. The Pierre Auger Observatory in Argentina and the Telescope Array (TA) in the US have reported their measurements of UHECR energy spectra observed in the southern and northern hemisphere, respectively. The region of the sky accessible to both Observatories ($[-15,+24]$ degrees in declination) can be used to cross-calibrate the two spectra. The Auger-TA energy spectrum working group was organized in 2012 and has been working to understand the uncertainties in energy scale in both experiments, their systematic differences, and differences in the shape of the spectra. In previous works, we reported that there was an overall agreement of the energy spectra measured by the two observatories below 10 EeV while at higher energies, a remaining significant difference was observed in the common declination band. We revisit this issue to understand its origin by examining the systematic uncertainties, statistical effects, and other possibilities. We will also discuss the differences in the spectra in different declination bands and a new feature in the spectrum recently reported by the Auger Collaboration.