Mass composition of ultrahigh-energy cosmic rays with the Telescope Array Surface Detector data

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, 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. Piskunov, M. S. Pshirkov, J. Remington, 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, M. Takeda, 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, K. Yada, 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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Abstract

The results on ultrahigh-energy cosmic rays (UHECR) mass composition obtained with the Telescope Array surface detector are presented. The analysis employs the Boosted Decision tree (BDT) multivariate analysis built upon 14 observables related to both the properties of the shower front and the lateral distribution function. The multivariate classifier is trained with Monte-Carlo sets of events induced by the primary protons and iron. An average atomic mass of UHECR is presented for energies 1018.0-1020.0 eV. The average atomic mass of primary particles shows no significant energy dependence and corresponds to lnA = 2.0±0.1(stat.)±0.44(syst.). The result is compared to the mass composition obtained by the Telescope Array with Xmax technique along with the results of other experiments. Possible systematic errors of the method are discussed.

Original languageEnglish
Article number022001
JournalPhysical Review D
Volume99
Issue number2
DOIs
Publication statusPublished - 2019 Jan 15

Bibliographical note

Funding Information:
The Telescope Array experiment is supported by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Priority Area 431, for Specially Promoted Research JP21000002, for Scientific Research (S) JP19104006, for Specially Promote Research JP15H05693, for Scientific Research (S) JP15H05741 and for Young Scientists (A) JPH26707011; by the joint research program of the Institute for Cosmic Ray Research (ICRR), The University of Tokyo; by the U.S. National Science Foundation Grants No. PHY-0601915, No. PHY-1404495, No. PHY-1404502, and No. PHY-1607727; by the National Research Foundation of Korea (2017K1A4A3015188, 2016R1A2B4014967, 2017R1A2A1A05071429, 2016R1A5A1013277); by IISN Project No. 4.4502.13, and Belgian Science Policy under IUAP VII/37 (ULB). The development and application of the multivariate analysis method is supported by the Russian Science Foundation Grant No. 17-72-20291 (INR). The foundations of Dr. Ezekiel R. and Edna Wattis Dumke, Willard L. Eccles, and George S. and Dolores Dore Eccles all helped with generous donations. The State of Utah supported the project through its Economic Development Board, and the University of Utah through the Office of the Vice President for Research. The experimental site became available through the cooperation of the Utah School and Institutional Trust Lands Administration (SITLA), U.S. Bureau of Land Management (BLM), and the U.S. Air Force. We appreciate the assistance of the State of Utah and Fillmore offices of the BLM in crafting the Plan of Development for the site. Patrick Shea assisted the collaboration with valuable advice on a variety of topics. The people and the officials of Millard County, Utah have been a source of steadfast and warm support for our work which we greatly appreciate. We are indebted to the Millard County Road Department for their efforts to maintain and clear the roads which get us to our sites. We gratefully acknowledge the contribution from the technical staffs of our home institutions. An allocation of computer time from the Center for High Performance Computing at the University of Utah is gratefully acknowledged. The cluster of the Theoretical Division of INR RAS was used for the numerical part of the work.

Funding Information:
The Telescope Array experiment is supported by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Priority Area 431, for Specially Promoted Research JP21000002, for Scientific Research (S) JP19104006, for Specially Promote Research JP15H05693, for Scientific Research (S) JP15H05741 and for Young Scientists (A)JPH26707011; by the joint research program of the Institute for Cosmic Ray Research (ICRR), The University of Tokyo; by the U.S. National Science Foundation Grants No.PHY-0601915, No.PHY-1404495, No.PHY-1404502, and No.PHY-1607727; by the National Research Foundation of Korea (2017K1A4A3015188, 2016R1A2B4014967, 2017R1A2A1A05071429, 2016R1A5A1013277); by IISN Project No.4.4502.13, and Belgian Science Policy under IUAP VII/37 (ULB). The development and application of the multivariate analysis method is supported by the Russian Science Foundation Grant No.17-72-20291 (INR). The foundations of Dr. Ezekiel R. and Edna Wattis Dumke, Willard L. Eccles, and George S. and Dolores Dore Eccles all helped with generous donations. The State of Utah supported the project through its Economic Development Board, and the University of Utah through the Office of the Vice President for Research. The experimental site became available through the cooperation of the Utah School and Institutional Trust Lands Administration (SITLA), U.S. Bureau of Land Management (BLM), and the U.S. Air Force. We appreciate the assistance of the State of Utah and Fillmore offices of the BLM in crafting the Plan of Development for the site. Patrick Shea assisted the collaboration with valuable advice on a variety of topics. The people and the officials of Millard County, Utah have been a source of steadfast and warm support for our work which we greatly appreciate. We are indebted to the Millard County Road Department for their efforts to maintain and clear the roads which get us to our sites. We gratefully acknowledge the contribution from the technical staffs of our home institutions. An allocation of computer time from the Center for High Performance Computing at the University of Utah is gratefully acknowledged. The cluster of the Theoretical Division of INR RAS was used for the numerical part of the work.

Publisher Copyright:
© 2019 American Physical Society.

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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