2023 Fiscal Year Final Research Report

Search for Ultra-High Energy Cosmic Ray origin using the extended Telescope Array experiment

Research Project

PDF

Project/Area Number	19KK0074
Research Category	Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 15:Particle-, nuclear-, astro-physics, and related fields
Research Institution	The University of Tokyo
Principal Investigator	Sako Takashi 東京大学, 宇宙線研究所, 准教授 (90324368)
Co-Investigator(Kenkyū-buntansha)	野中敏幸東京大学, 宇宙線研究所, 助教 (30506754) 木戸英治国立研究開発法人理化学研究所, 開拓研究本部, 研究員 (00633778) 藤井俊博京都大学, 白眉センター, 特定助教 (50706877)
Project Period (FY)	2019-10-07 – 2024-03-31
Keywords	宇宙線 / アマテラス粒子 / 粒子加速 / 銀河系外天体 / 空気シャワー実験
Outline of Final Research Achievements	Stable operation of the extended surface detectors of the Telescope Array experiment was achieved. Although the initial adjustments and maintenance were delayed due to travel restrictions during the COVID-19 pandemic, this was accomplished through the task sharing with the University of Utah and online discussions. The energy spectrum derived from the extended part was successfully measured, showing consistency with previous research. The original Telescope Array experiment continued to operate, and in May 2021, it successfully observed the second-highest energy cosmic ray in history. This event, named the "Amaterasu Particle," garnered attention from media worldwide and brought significant attention to cosmic ray research. Analysis of arrival directions, considering the cosmic magnetic field, also progressed and was applied to understand the impact on correlations with starburst galaxies and the interpretation of the origin of the Amaterasu Particle.
Free Research Field	宇宙線物理学
Academic Significance and Societal Importance of the Research Achievements	宇宙から10ジュールにも相当するエネルギーを持つ超高エネルギー宇宙線が到来していることは現代物理学の最大の謎のひとつである。本研究を通してテレスコープアレイ実験が2021年に観測した、史上2番目にエネルギーの高い宇宙線（通称アマテラス）の報告は、日本のみならず世界で高い関心を集めた。観測能力を向上した拡張テレスコープアレイの安定運用が本研究によって成功したことで、アマテラスのような驚くべき自然現象を今後も発見し、物理学の基本問題の解明に挑み社会の期待に応えることができる。