Observation of spectral structures in the flux of cosmic ray protons with CALET on the International Space Station
Creators: name: Kobayashi, Kazuyoshi
name: Adriani, Oscar
name: Akaike, Yosui
name: Asano, Katsuaki
name: Aaoka, Yoichi
name: Berti, Eugenio
name: Bigongiari, Gabriele
name: Binns, Walter Robert
name: Bongi, Massimo
name: Brogi, Paolo
name: Bruno, Alessandro
name: Cannady, Nicholas
name: Castellini, Guide
name: Checchia, Caterina
name: Cherry, Walter Robert
name: Collazuol, Gianmaria
name: De Nolfo, Georgia A.
name: Ebisawa, Ken
name: Ficklin, Anthony W.
name: Fuke, Hideyuki
name: Gonzi, Sandro
name: Guzik, T. Gregory
name: Hams, Thomas
name: Hibino, Kinya
name: Ichimura, Masakatsu
name: Ioka, Kunihito
name: Ishizaki, Wataru
name: Israel, Martin H.
name: Kasahara, Katsumasa
name: Kataoka, Jun
name: Kataoka, Ryuho
name: Katayose, Yusaku
name: Kato, Chihiro
name: Kawanaka, Norita
name: Kawakubo, Yuta
name: Kobayashi, Kenko
name: Kohri, Kazunori
name: Krawczynski, Henric S.
name: Krizmanic, John F.
name: Maestro, Paolo
name: Marrocchesi, Pier Simone
name: Messineo, Alberto Maria
name: Mitchell, Jason W.
name: Miyake, Shoko
name: Moiseev, Alexander
name: Mori, Masaki
name: Mori, Nicola
name: Motz, Holger Martin
name: Munakata, Kazuoki
name: Nakahira, Satoshi
name: Nishimura, Jun
name: Okuno, Shoji
name: Ormes, Jonathan
name: Ozawa, Shunsuke
name: Pacini, Lorenzo
name: Pacini, Paolo
name: Rauch, Brian Flint
name: Ricciarini, Ricciarini
name: Sakai, Kazuhiro
name: Sakamoto, Takanori
name: Sasaki, Makoto
name: Shimizu, Yuki
name: Shiomi, Atsushi
name: Spillantini, Piero
name: Stolzi, Francesco
name: Sugita, Satoshi
name: Sulaj, Arta
name: Takita, Masato
name: Tamura, Tadahisa
name: Terasawa, Toshio
name: Torii, Shoji
name: Tsunesada, Yoshiki
name: Uchihori, Yukio
name: Vannuccini, Elena
name: Wefel, John P.
name: Yamaoka, Kazutaka
name: Yanagita, Shohei
name: Yoshida, Atsumasa
name: Yoshida, Kenji
name: Zober, Wolfgang V.
Publisher: name: Proceedings of Science
Year: 2023

description: 38th International Cosmic Ray Conference (ICRC2023), 26 July - 3 August, 2023, Nagoya, Japan
description: A precise measurement of the cosmic-ray proton spectrum is carried out with the Calorimetric Electron Telescope (CALET) and a sharp softening of the energy spectrum above 10 TeV is observed. CALET, located on the International Space Station, has started data taking in October 2015 and has accumulated data for more than seven years without any serious troubles. CALET is pursuing the direct measurement of the main components of high energy cosmic rays up to ~1 PeV in order to understand the cosmic ray acceleration and propagation. Thanks to the thick calorimeter that corresponds to 30 radiation lengths and to \sim1.3 proton interaction lengths, the proton analysis presented in this paper spans a broad energy range from 50 GeV to 60 TeV. Proton energy resolution is 30-40%, and the residual background is less than 10% in the E &lt; 10 TeV region. In the multi-TeV region, we observed a spectral softening with a spectral index change from -2.6 to -2.9 in addition to the spectral hardening we had previously confirmed with a high significance above a few hundred GeV. The transition to the softer regime is much sharper than the smooth onset of hardening observed at lower energy.