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2019 Fiscal Year Final Research Report

Measurement of the proton radius by a precision laser spectroscopy of muonic hydrogen atom

Research Project

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Project/Area Number 18K13572
Research Category

Grant-in-Aid for Early-Career Scientists

Allocation TypeMulti-year Fund
Review Section Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
Research InstitutionHigh Energy Accelerator Research Organization (2019)
Institute of Physical and Chemical Research (2018)

Principal Investigator

KANDA Sohtaro  大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 助教 (10800485)

Project Period (FY) 2018-04-01 – 2020-03-31
Keywordsミュオン / レーザー / ミュオン水素原子 / レーザー分光 / 陽子半径
Outline of Final Research Achievements

In this study, we aimed at laser spectroscopy of the hyperfine structure of the muonic hydrogen atom in the ground state to determine the proton Zemach radius. The main results obtained are the following two. (1) We developed a high-intensity mid-infrared pulsed laser as a transition light source, and developed a narrow linewidth and high-power quantum cascade laser that oscillates at a wavelength of 6.8 μm. Furthermore, we have developed a multi-reflection cell with high reflectivity in the mid-infrared region. (2) We established the μ-SR method with low-pressure gaseous hydrogen, and succesfully observed the muon spin rotation of muon hydrogen and muon deuterium atoms in a transverse magnetic field. With these results, the realization of the experiment became realistic.

Free Research Field

素粒子・原子核・原子物理学

Academic Significance and Societal Importance of the Research Achievements

陽子の電荷半径が測定によって異なる「陽子の半径問題」は素粒子・原子核・原子物理学における重要な未解決問題であり、その解決は学術的な急務である。本研究ではこれに従来法とは異なるアプローチで取り組み、実験に不可欠な装置の開発と手法の原理実証に成功した。本研究において開発した大強度の中赤外パルスレーザーは前例のない波長領域で大強度かつ狭線幅を実現し、微細加工や低侵襲治療への応用が可能である。低圧の気体標的を用いた負ミュオンによるミュオンスピン回転法は原子核・原子物理学および放射化学における重要な基礎技術となるもので今後の多方面への展開が期待される。

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Published: 2021-02-19  

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