Development of the neutron polarization device for the CP-violation search

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K14495
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Nagoya University
• Principal Investigator: Okudaira Takuya 名古屋大学, 理学研究科, 助教 (40826129)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 偏極中性子 / 核偏極 / CP対称性の破れ

Outline of Final Research Achievements

We have developed a neutron beam spin-polarization device: a 3He spin filter, which is indispensable for the CP violation search using a neutron absorption reaction by nuclei. The 3He spin filter is a device to polarize a neutron beam by using neutron absorption reaction of polarized 3He nuclei. A laser system for polarizing 3He gas was constructed at J-PARC, and it was confirmed that a high 3He polarization of about 80% can be achieved. An angular distribution of gamma-rays emitted from the polarized neutron absorption reaction by nuclei and a spin dependent absorption cross section of polarized La and polarized neutrons were successfully measured using this device.

Free Research Field

素粒子原子核物理

Academic Significance and Societal Importance of the Research Achievements

開発した3Heスピンフィルタを用いて世界最大強度を誇るJ-PARCの中性子ビームを幅広いエネルギー領域において偏極することに成功した。本デバイスを用いて測定した原子核の中性子断面積のスピン依存性から139LaにおけるCP対称性の破れの増幅率を決定することに成功した。これはCP対称性の破れ探索に対して非常に大きなマイルストーンである。本デバイスはCP対称性の破れ探索のみならず中性子ビームを用いた広範な科学領域にわたり高い有用性を持つことから、今後様々な中性子実験に応用させることが期待される。