2018 Fiscal Year Final Research Report

A large-scale darkmatter direct-detection experiment

Planned Research

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Project Area	Revealing the history of the universe with underground particle and nuclear research
Project/Area Number	26104004
Research Category	Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
Allocation Type	Single-year Grants
Review Section	Science and Engineering
Research Institution	The University of Tokyo
Principal Investigator	KISHIMOTO Yasuhiro 東京大学, 宇宙線研究所, 准教授 (30374911)
Co-Investigator(Kenkyū-buntansha)	小川洋日本大学, 理工学部, 助手 (20374910) 小林兼好東京大学, 宇宙線研究所, 特任助教 (70466861) 市村晃一東京大学, 宇宙線研究所, 特任助教 (80600064) 梁炳守東京大学, 宇宙線研究所, 特任助教 (10626055)
Research Collaborator	ABE Ko SUZUKI Yoichiro
Project Period (FY)	2014-07-10 – 2019-03-31
Keywords	暗黒物質 / 極低放射能技術
Outline of Final Research Achievements	In order to address to one of the biggest mysteries in the universe, the dark matter, this research project has challenged two tasks: dark matter search with a large-scale experimental apparatus, and development and research of a next-generation dark matter search apparatus. As for the first subject, in this study, we searched for the seasonal modulation signal by dark matter, which the previous research (DAMA / LIBRA) claims, and denied the result. In addition, we searched for dark matter candidates called Bosonic-Super WIMPs, and for the first time published the conclusion that "the vector type cannot be the main component of dark matter". For the second issue, we developed and improved ultra-low background technology.
Free Research Field	天体素粒子物理学
Academic Significance and Societal Importance of the Research Achievements	我々は，宇宙の物質の約２０％しか知らない．残り約８０％は未知の暗黒物質で占められている．この正体を解明すること無しに，宇宙を知ったとは言えない．本研究は，この暗黒物質の正体を解明すべく，大型実験装置XMASSを用いて探索を行った．先行研究（DAMA/LIBRA実験）では，標準的な暗黒物質が引き起こす季節変動事象が観測されていたが，本実験はその結果を大統計で追試し，「そのような季節変動はない」と結論づけた．暗黒物質が何か？この謎にたいする答えは，将来の実験に委ねられることとなったが，そこでは，本研究で開発した極低バックグラウンドの成果が応用されると期待される．．