Isotropy of Cosmic Rays beyond <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mn>10</mml:mn><mml:mn>20</mml:mn></mml:msup><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>eV</mml:mi></mml:math> Favors Their Heavy Mass Composition
Rashid Abbasi, Yasuaki Abe, T. Abu-Zayyad, M. Allen, Y. Arai, R. Arimura, E. Barcikowski, John Belz, D. R. Bergman, S. A. Blake, I. Buckland, B. G. Cheon, M. Chikawa, Toshihiro Fujii, Kozo Fujisue, K. Fujita, Ryo Fujiwara, M. Fukushima, G. Furlich, Noémie Globus, R. Gonzalez, W. Hanlon, N. Hayashida, H. H. He, R. Hibi, K. Hibino, R. Higuchi, K. Honda, D. Ikeda, N. Inoue, T. Ishii, H. Ito, D. Ivanov, A. Iwasaki, H. M. Jeong, Sohee Jeong, C. C. H. Jui, K. Kadota, F. Kakimoto, O. Kalashev, K. Kasahara, Saori Kasami, S. Kawakami, K. Kawata, I. Kharuk, E. Kido, H. B. Kim, J. H. Kim, J. H. Kim, S. W. Kim, Yasuhisa Kimura, I. Komae, V. Kuzmin, M. Kuznetsov, Youngshin Kwon, K. H. Lee, B. Lubsandorzhiev, Jon Paul Lundquist, H. Matsumiya, Tomoyuki Matsuyama, J. N. Matthews, R. Mayta, Koji Mizuno, Masao Murakami, I. Myers, K. H. Lee, S. Nagataki, Katsunori Nakai, T. Nakamura, E. Nishio, T. Nonaka, Hiroyuki Oda, S. Ogio, M. Onishi, H. Ohoka, N. Okazaki, Yuya Oku, T. Okuda, Y. Omura, Masaaki Ono, A. Oshima, H. Oshima, Seiji Ozawa, I. H. Park, K. Y. Park, M. Potts, М. С. Пширков, J. Remington, D. C. Rodriguez, C. Rott, G. I. Rubtsov, D. Ryu, H. Sagawa, Ryosuke Saito, Н. Сакаки, T. Sako, N. Sakurai, Daisuke Sato, Kousuke Sato, S. Sato
Abstract
We report an estimation of the injected mass composition of ultrahigh energy cosmic rays (UHECRs) at energies higher than 10 EeV. The composition is inferred from an energy-dependent sky distribution of UHECR events observed by the Telescope Array surface detector by comparing it to the Large Scale Structure of the local Universe. In the case of negligible extragalactic magnetic fields (EGMFs), the results are consistent with a relatively heavy injected composition at E∼10 EeV that becomes lighter up to E∼100 EeV, while the composition at E>100 EeV is very heavy. The latter is true even in the presence of highest experimentally allowed extragalactic magnetic fields, while the composition at lower energies can be light if a strong EGMF is present. The effect of the uncertainty in the galactic magnetic field on these results is subdominant.