1. The Cosmic-Ray Composition between 2 PeV and 2 EeV Observed with the TALE Detector in Monocular Mode
- Author
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BayarJon Paul Lubsandorzhiev, Mayuko Minamino, K. Honda, Masaaki Tanaka, Ryuji Takeishi, Hiroyuki Sagawa, Yasunori Saito, Pierre Sokolsky, B. K. Shin, M. Takeda, M. Yamamoto, Shigehiro Nagataki, R. Sahara, Toshiyuki Fujii, Shingo Kawana, William Hanlon, T. Okuda, J. Yang, M. Allen, Seok Ho Jeong, Nobuyuki Sakurai, K. H. Lee, T.-A. Shibata, Shoichi Kishigami, Yuichiro Tameda, John N. Matthews, Zach Zundel, T. Suzawa, Fugo Yoshida, Gordon Thomson, Tom Stroman, Fumiya Shibata, Ryota Onogi, Saori Kasami, D. Ikeda, Robert Cady, S. W. Kim, Ryosuke Tsuda, Isaac Myers, Hidemi Ito, R. Mayta, Masaomi Ono, H. Kawai, K. Kawata, N. Inoue, B. G. Cheon, Katsuaki Kasahara, J. H. Kim, Takashi Sako, T. Seki, Kiyoshi Tanaka, Koichi Sekino, M. Ohnishi, Min Hyo Kim, Takayuki Tomida, Grigory Rubtsov, Hideki Tanaka, Peter Tinyakov, Samuel Blake, Toshiyuki Nonaka, Taichi Inadomi, Norimichi Shibata, Y. Omura, Hideaki Shimodaira, Hyoming Jeong, Shoichi Ogio, Younghoon Kwon, Inkyu Park, John Belz, T. Matsuyama, Ryo Higuchi, Ryota Fukushima, S. Ozawa, Katsuya Yamazaki, Y. Nakamura, Federico R. Urban, Heungsu Shin, Kohei Yada, S. Kawakami, Keitaro Fujita, Y. Takahashi, Mai Takamura, Elliott Barcikowski, R. U. Abbasi, Y. Uchihori, Kei Nakai, Maxim Pshirkov, Dmitri Ivanov, S. Udo, C. C. H. Jui, Koki Sato, Tiffany Wong, Yuto Arai, Keijiro Mukai, Hiroyuki Matsumiya, Masaki Fukushima, Yusuke Kimura, Akimichi Taketa, Yuta Tanoue, Ryota Fujiwara, M. Chikawa, Takafumi Uehama, Tareq Abu-Zayyad, Motoki Hayashi, G. Furlich, Takaaki Ishii, J. P. Lundquist, Jyunsei Chiba, Naoto Sakaki, Daiki Shinto, Eiji Kido, M. V. Kuznetsov, Kazuhiro Machida, D. C. Rodriguez, Kozo Fujisue, Kengo Sano, Priti Shah, Dongsu Ryu, S. B. Thomas, Hirokazu Iwakura, Y. Takagi, Igor Tkachev, Naohiro Sone, H. Oda, Kenta Yashiro, Masato Takita, F. Kakimoto, Hongsu Kim, Sergey Troitsky, J. Remington, Naoaki Hayashida, Akitoshi Oshima, Y. Tsunesada, Ben Stokes, Y. Zhezher, Hideyuki Ohoka, Vladim Kuzmin, Toru Nakamura, Kenichi Kadota, M. Abe, Yuya Oku, Oleg Kalashev, Ryo Nakamura, D. R. Bergman, K. Hibino, H. Tokuno, and J. D. Smith
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Astroparticle physics ,Physics ,Monocular ,Astrophysics::High Energy Astrophysical Phenomena ,Detector ,Mode (statistics) ,FOS: Physical sciences ,Astronomy and Astrophysics ,Cosmic ray ,Astrophysics ,030226 pharmacology & pharmacy ,01 natural sciences ,03 medical and health sciences ,0302 clinical medicine ,Space and Planetary Science ,0103 physical sciences ,Astrophysics - High Energy Astrophysical Phenomena ,010303 astronomy & astrophysics - Abstract
We report on a measurement of the cosmic ray composition by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector (FD). By making use of the Cherenkov light signal in addition to air fluorescence light from cosmic ray (CR) induced extensive air showers, the TALE FD can measure the properties of the cosmic rays with energies as low as $\sim 2$ PeV and exceeding 1 EeV. In this paper, we present results on the measurement of $X_{\rm max}$ distributions of showers observed over this energy range. Data collected over a period of $\sim 4$ years was analyzed for this study. The resulting $X_{\rm max}$ distributions are compared to the Monte Carlo (MC) simulated data distributions for primary cosmic rays with varying composition and a 4-component fit is performed. The comparison and fit are performed for energy bins, of width 0.1 or 0.2 in $\log_{10} (E/{\rm eV})$, spanning the full range of the measured energies. We also examine the mean $X_{\rm max}$ value as a function of energy for cosmic rays with energies greater than $10^{15.8}$ eV. Below $10^{17.3}$ eV, the slope of the mean $X_{\rm max}$ as a function of energy (the elongation rate) for the data is significantly smaller than that of all elements in the models, indicating that the composition is becoming heavier with energy in this energy range. This is consistent with a rigidity-dependent cutoff of events from galactic sources. Finally, an increase in the $X_{\rm max}$ elongation rate is observed at energies just above $10^{17}$ eV indicating another change in the cosmic rays composition., 20 pages, 22 figures, accepted for publication in ApJ
- Published
- 2021