Effects of fission to isotopic abundances on the r-process synthesis in star

• Project/Area Number: 18K03631
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 15010:Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: Hiroyuki Koura 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 原子力科学研究所 先端基礎研究センター, 室長 (50391264)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Project Status: Completed (Fiscal Year 2021)
• Budget Amount: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000); Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000); Fiscal Year 2019: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2018: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
• Keywords: 原子核崩壊 / β崩壊 / 核分裂 / r過程元素合成 / 超重核 / 原子核の存在限界

Outline of Final Research Achievements

In the program, we performed a theoretical calculation related to nuclear fission on the r-process nucleosynthesis in explosive stellar phenomena for understanding the origin of chemical elements. We adopted the Koura-Tachibana-Uno-Yamada (KTUY) nuclear mass model for the calculation, and applied for the beta-delayed fission probabilities. We found that there are three regions as fission-favorable in the unknown superheavy nuclear mass region, while there is a region as fission-hindered near one of the doubly-magic nuclei, [126]-354.

Academic Significance and Societal Importance of the Research Achievements

我々の身の回りに存在する元素は宇宙の始まりから全てあったわけではなく、１３８億年の時を経て作られていった。その成り立ちは決して自明ではなく、原子物理、原子核物理、天体物理、宇宙物理の進展のなかで明らかになっていったのである。その観点で見ると、本課題の爆発的天体環境下で起こるとされた元素合成（r過程と呼ぶ）はそれに関わる原子核のほとんどが実験的に未知であり、その解明は「我々はどのようにして存在したのか」という問いに大きく迫るものである。
本課題は「超重核」で重要とされている核分裂現象がr過程でも有意に影響を及ぼすことを示したものであり、両研究を結びつける意義のある研究成果である。

Research Products

• [Journal Article] Ground-state β-decay spectroscopy of Ta-187 (2022)
  • Author(s): Mukai M.、Hirayama Y.、Watanabe Y. X.、Watanabe H.、Koura H.、Jeong S. C.、Miyatake H.、Brunet M.、Ishizawa S.、Kondev F. G.、Lane G. J.、Litvinov Yu. A.、Niwase T.、Oyaizu M.、Podolyak Zs.、Rosenbusch M.、Schury P.、Wada M.、Walker P. M.
  • Journal Title: Physical Review C Volume: 105 Issue: 3 Pages: 034331-034331
  • DOI: 10.1103/physrevc.105.034331
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Masses of exotic nuclei (2021)
  • Author(s): Yamaguchi T.、Koura H.、Litvinov Yu.A.、Wang M.
  • Journal Title: Progress in Particle and Nuclear Physics Volume: 120 Pages: 103882-103882
  • DOI: 10.1016/j.ppnp.2021.103882
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] First high-precision direct determination of the atomic mass of a superheavy nuclide (2021)
  • Author(s): Schury P.、Niwase T.、Wada M.、Brionnet P.、Chen S.、Hashimoto T.、Haba H.、Hirayama Y.、Hou D. S.、Iimura S.、Ishiyama H.、Ishizawa S.、Ito Y.、Kaji D.、Kimura S.、Koura H.、Liu J. J.、Miyatake H.、Moon J.-Y.、Morimoto K.、Morita K.、Nagae D.、Rosenbusch M.、Takamine A.、Watanabe Y. X.、Wollnik H.、Xian W.、Yan S. X.
  • Journal Title: Physical Review C Volume: 104 Issue: 2
  • DOI: 10.1103/physrevc.104.l021304
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Analysis of nuclear structure in the nuclear chart and improvement to the gross theory of β decay (2019)
  • Author(s): Fumitaka Endo and Hiroyuki Koura
  • Journal Title: Physical Review C Volume: 99
  • Peer Reviewed
• [Presentation] 原子核質量から見た原子核の大域的な性質とr過程元素合成 (2019)
  • Author(s): 小浦寛之
  • Organizer: 原子核物理でつむぐrプロセス（京都大学基礎物理学研究所）
  • Invited
• [Presentation] Global properties of nuclei in the nuclear chart relevant to r-process nucleosynthesis (2019)
  • Author(s): H. Koura
  • Organizer: The international workshop on nuclear physics for astrophysical phenomena ( Tokyo Tech, 23-25)
  • Int'l Joint Research / Invited
• [Presentation] 超重核領域における核分裂が主要となる領域の分布 (2019)
  • Author(s): 小浦寛之、遠藤史隆
  • Organizer: 日本物理学会2019年秋季大会（山形大学）
• [Presentation] Systematical calculation of probabilities of beta-delayed neutron emission and fission in the entire region of nuclear chart (2019)
  • Author(s): H. Koura and F. Endo
  • Organizer: The 2019 Symposium on Nuclear Data, Nov. 27-28, 2019, Fukuoka, Kyushu
• [Presentation] Effect of fission process in the super- and super-heavy nuclei to the r-process nucleosynthesis (2019)
  • Author(s): H. Koura and F. Endo
  • Organizer: The fourth International Symposium on Superheavy elements (SHE2019) , Dec. 1-5, 2019, Hakone, Kanagawa
  • Int'l Joint Research
• [Presentation] 中性子過剰な重・超重核領域におけるβ崩壊の禁止遷移の役割 (2019)
  • Author(s): 小浦寛之、遠藤史隆
  • Organizer: 日本物理学会第74回年次大会
• [Presentation] 原子核質量と r 過程元素合成 (2019)
  • Author(s): 小浦寛之
  • Organizer: 核データと重元素合成を中心とする宇宙核物理研究会（宇宙核物理連絡協議会・北大主催）
  • Invited
• [Book] ニホニウム (2021)
  • Author(s): 須藤 彰三、岡 真、小浦 寛之
  • Total Pages: 266
  • Publisher: 共立出版
  • ISBN: 9784320035447