Development of techniques for epi-thermal polarized neutrons and determination of enhancement of CP-violation in 139La

• Project/Area Number: 19K21047
• Project/Area Number (Other): 18H05864 (2018)
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund (2019); Single-year Grants (2018)
• Review Section: 0203:Particle-, nuclear-, astro-physics, and related fields
• Research Institution: Nagoya University (2020); Japan Atomic Energy Agency (2018-2019)
• Principal Investigator: Okudaira Takuya 名古屋大学, 理学研究科, 助教 (40826129)
• Project Period (FY): 2018-08-24 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000); Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: 原子核反応 / (n,γ)反応 / 中性子 / 中性子偏極 / 3He核偏極 / CP対称性の破れ / 中性子偏極デバイス / 中性子ビーム / 偏極中性子 / 核偏極 / 原子核 / 複合核 / 原子核(実験) / 3Heスピンフィルター

Outline of Research at the Start

139Laの中性子吸収反応では基本相互作用におけるCP対称性の破れが百万倍以上増幅されていることが近年明らかになった。これにより未知のCP対称性の破れを今までにない感度で探索できる可能性が示唆され、国内外で注目されている。一方でCP対称性の破れの増幅率には未だ不定性があり、これを最終的に決定することが本研究の目的である。本研究では中性子偏極デバイス:3Heスピンフィルターの高性能化を行い、従来は偏極が難しかったeV領域の中性子偏極を達成する。これを用いて、139Laの偏極中性子吸収反応に伴って放出されるγ線の放出方向のアシンメトリを測定し、139LaのCP対称性の破れ増幅率を決定する。

Outline of Final Research Achievements

The objective of this research is to determine an enhancement factor of the CP-violation in compound nuclei of 139La+n by measuring an angular distribution of gamma-rays emitted in polarized neutron absorption reactions of 139La.
First, We developed high quality 3He spin filters in J-PARC to polarize a neutron beam. Then, the 3He spin filter was installed to a neutron beam line ANNRI, and the angular distribution of gamma-rays were measured with a germanium detector assembly. As a result, the angular distribution of gamma-rays depending on the neutron spin direction was found in the transition from 139La+n state to ground state of 140La. The theoretical study to interpret this result is now ongoing with collaborators.

Academic Significance and Societal Importance of the Research Achievements

現在我々の宇宙には反物質はほとんど存在せず、物質のみで構成されている。これを説明するためには既存の理論体系を超えるようなCP対称性の破れが存在しているはずであるが、未だ未発見である。本研究は原子核の中性子吸収反応時にCP対称性の破れが増幅される現象を利用して、未知の物理現象探す計画の一環であり、原子核内におけるCP対称性の破れの増幅率の決定に大きく貢献する。
また、本研究で開発した中性子ビームの偏極技術は物性研究や、生命科学、工学など様々な分野への応用が可能である。特に1eV程度のエネルギーが高い中性子の偏極がJ-PARCで実現されたことは今後の中性子科学の発展に大きく貢献するものである。

Research Products

• [Journal Article] Current status of development of a 3He spin filter for user experiments at J-PARC (2021)
  • Author(s): T. Okudaira, T. Oku, K. Sakai, I. Ino, H. Hayashida, K. Hiroi, T. Shinohara, K. Kakurai, K. Aizawa
  • Journal Title: Japan physics journal web of conferences Volume: 33
  • DOI: 10.7566/jpscp.33.011087
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Transverse asymmetry of γ rays from neutron-induced compound states of La140 (2020)
  • Author(s): Yamamoto T.、Okudaira T.、Endo S.、Fujioka H.、Hirota K.、Ino T.、Ishizaki K.、Kimura A.、Kitaguchi M.、Koga J.、Makise S.、Niinomi Y.、Oku T.、Sakai K.、Shima T.、Shimizu H. M.、Takada S.、Tani Y.、Yoshikawa H.、Yoshioka T.
  • Journal Title: Physical Review C Volume: 101 Issue: 6 Pages: 064624-064624
  • DOI: 10.1103/physrevc.101.064624
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Development of the neutron polarizer for the T-violation search using compound nuclei (2020)
  • Author(s): Okudaira Takuya
  • Journal Title: Proceedings of Science Volume: KMI2019 Pages: 029-029
  • DOI: 10.22323/1.356.0029
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Development and application of a 3He Neutron Spin Filter at J-PARC (2020)
  • Author(s): Okudaira T.、Oku T.、Ino T.、Hayashida H.、Kira H.、Sakai K.、Hiroi K.、Takahashi S.、Aizawa K.、Endo H.、Endo S.、Hino M.、Hirota K.、Honda T.、Ikeda K.、Kakurai K.、Kambara W.、Kitaguchi M.、Oda T.、Ohshita H.、Otomo T.、Shimizu H.M.、Shinohara T.、Suzuki J.、Yamamoto T.
  • Journal Title: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Volume: 977 Pages: 164301-164301
  • DOI: 10.1016/j.nima.2020.164301
  • NAID: 120006882449
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] ransverse asymmetry of γ rays from neutron-induced compound states of 140La (2019)
  • Author(s): T. Yamamoto, T. Okudaira, S. Endo, H. Fujioka, K. Hirota, T. Ino, K. Ishizaki, A. Kimura, M. Kitaguchi, J. Koga, S. Makise, Y. Niinomi, T. Oku, K. Sakai, T. Shima, H. M. Shimizu, S. Takada, Y. Tani, H. Yoshikawa, T. Yoshioka
  • Journal Title: arXiv Volume: nucl-ex
  • Open Access
• [Journal Article] Measurement of the angular distribution of γ-rays after neutron capture by 139La for a T-violation search (2019)
  • Author(s): Okudaira Takuya et al.
  • Journal Title: EPJ Web of Conferences Volume: 219 Pages: 09001-09001
  • DOI: 10.1051/epjconf/201921909001
  • Peer Reviewed / Open Access
• [Journal Article] Verification of the compound nuclear model for T-violation search (2019)
  • Author(s): Yamamoto Tomoki、Shimizu Hirohiko M.、Ishizaki K.、Niinomi Y.、Kitaguchi Masaaki、Takada Shunsuke、Koga Jun、Makise S.、Yoshioka Tamaki、Kimura Atsushi、Sakai Kenji、Oku T.、Okudaira Takuya、Endo Shun、Tani Y.、Fujioka Hiroyuki、Yoshikawa H.、Hirota Katsuya、Shima Tatsushi
  • Journal Title: POS Volume: KMI2019 Pages: 42-42
  • DOI: 10.22323/1.356.0042
  • Peer Reviewed / Open Access
• [Journal Article] Measurement of Angular Distributions in 139La(n,gamma) Reaction for T Violation Search (2018)
  • Author(s): Okudaira T.、Shimizu H. M.、Kitaguchi M.、Hirota K.、Haddock C. C.、Oi N.、Ito I.、Yamamoto T.、Endo S.、Takada S.、Koga J.、Yoshioka T.、Ino T.、Asahi K.、Momose T.、Iwata T.、Sakai K.、Oku T.、Kimura A.、Hino M.、Shima T.、Yamagata Y.
  • Journal Title: Proceedings of the International Conference on Neutron Optics (NOP2017) Volume: 22 Pages: 011041-011041
  • DOI: 10.7566/jpscp.22.011041
  • Peer Reviewed / Open Access
• [Presentation] 複合核共鳴における時間反転対称性の破れ探索に向けた偏極中性子による139La(n,γ)反応の解析 (2020)
  • Author(s): 山本 知樹
  • Organizer: 日本物理学会秋季大会
• [Presentation] JAEAにおける3He中性子スピンフィルターの開発 (2020)
  • Author(s): 奥平琢也
  • Organizer: 量子ビームサイエンスフェスタ
• [Presentation] J-PARCにおける3He スピンフィルターの開発と利用 (2020)
  • Author(s): 奥平琢也
  • Organizer: 日本中性子科学会
• [Presentation] 中性子偏極のための3Heスピンフィルターの開発の現状 (2020)
  • Author(s): 奥平琢也
  • Organizer: 日本物理学会秋季大会
• [Presentation] Polarized pulsed neutrons using a 3He spin filter with an in-site SEOP method (2019)
  • Author(s): Takuya Okudaira et al.
  • Organizer: European Conference on Neutron Scattering
  • Int'l Joint Research
• [Presentation] Development and applications of a 3He spin filter for utilization of polarized neutrons (2019)
  • Author(s): Takuya Okudaira et al.
  • Organizer: J-PARC symposium 2019
  • Int'l Joint Research
• [Presentation] Development of the neutron polarizer for T-violation search using compound nuclei (2019)
  • Author(s): Takuya Okudaira et al.
  • Organizer: KMI2019
  • Int'l Joint Research
• [Presentation] Development of the neutron polarizer for the T-violation search using compound nuclei (2019)
  • Author(s): T. Okudaira, T. Oku, K. Sakai, T. Ino, H. Hayashida, K. Hiroi, T. Shinohara, K. Kakurai, K. Aizawa, H. M. Shimizu, M. Kitaguchi , T. Yamamoto
  • Organizer: The 4th KMI International Symposium
  • Int'l Joint Research
• [Presentation] 複合核における時間反転対称性の破れ探索に向けた中性子偏極デバイスの開発 (2019)
  • Author(s): 奥平琢也, 奥隆之, 酒井健二, 廣井孝介, 篠原武尚, 相澤一也, 猪野隆, 林田洋寿, 加倉井和久, 清水裕彦, 北口雅暁, 山本知樹, 佐藤匠, 新實裕大
  • Organizer: 日本物理学会
• [Presentation] Measurement of the angular distribution of γ-rays from neutron-induced compound states of 139La for T-Violation Search (2018)
  • Author(s): T.Okudaira, H.M.Shimizu, M.Kitaguchi, K.Hirota, C.C.Haddock, I.Ito, T.Yamamoto, S.Endo, K.Ishizaki, T.Sato, S.Takada, J.Koga, T.Yoshioka, T.Ino, K.Asahi, T.Momose, T.Iwata, K.Sakai, T.Oku, A.Kimura, T.Nakao, M.Hino, T.Shima, Y.Yamagata
  • Organizer: International Workshop on Particle physics at Neutron Sources
  • Int'l Joint Research
• [Presentation] Studying discrete symmetry violation in neutron-nucleus system (2018)
  • Author(s): Takuya Okudaira
  • Organizer: 5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
  • Int'l Joint Research / Invited
• [Presentation] JAEAにおける 偏極3He中性子スピンフィルター開発の現状 (2018)
  • Author(s): 奥平琢也 奥隆之, 酒井健二, 猪野隆, 林田洋寿, 廣井孝介, 篠原武尚, 加倉井和久, 相澤一也
  • Organizer: 日本中性子科学会