Search for cosmic PeV particle accelerators using a new cosmic-ray observatory in Andes highland

2023 Fiscal Year Final Research Report

• Project/Area Number: 19H00678
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• 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): 日比野 欣也 神奈川大学, 工学部, 教授 (80260991)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 宇宙線 / 最高エネルギーガンマ線 / 空気シャワーアレイ実験 / 天の川銀河

Outline of Final Research Achievements

A new cosmic-ray air shower array, ALPAQUITA, is installed in the Bolivian Andes at the altitude of 4,740m. The array operation started smoothly and we obtained an expected angular resolution. Occultation of the cosmic-ray flux by the moon, so-called "moon's shadow" is also observed. We searched for a gamma-ray emission from a supernova remnant RX J1713.7-3946 and obtained its flux upper limits. At around 200TeV, the upper limit is comparable to the one by the most sensitive previous work.
The design of the underground muon detector to improve the sensitivity to gamma-rays is fixed and waiting a construction. Once constructed, ALPAQUITA + 1MD will have a 1-year sensitivity to detect some gamma-ray sources know in the TeV range.

Free Research Field

宇宙線物理学

Academic Significance and Societal Importance of the Research Achievements

南半球で初めてとなる高地での本格的宇宙線空気シャワーアレイを設置し、期待通りの性能で運用を開始した。設計が完了した地下ミュー粒子検出器を建設することで銀河系中心方向のsub-PeVガンマ線放射天体の分布、特性を世界で初めて明らかにできる。これは、宇宙物理学100年以上の課題である、銀河系宇宙線起源の解明につながる成果となる。