2026-04-08 大阪大学
今回の研究で新たに開発した実験セットアップ。WASA検出器で η′中間子原子核の崩壊から出る陽子を検出し、前方の重陽子の運動エネルギーを破砕核分離装置 (FRS) で精密に測定した。
＜関連情報＞
- https://www.sci.osaka-u.ac.jp/ja/topics/16622/
- https://www.sci.osaka-u.ac.jp/ja/wp-content/uploads/2020/08/pr_itahashi.pdf
- https://journals.aps.org/prl/abstract/10.1103/6vsl-ng7x
励起スペクトル12C（p、d）付近での反応η′高運動量陽子との同時測定による中間子放出閾値の測定 Excitation Spectra of the 12C(p,d) Reaction near the η′-Meson Emission Threshold Measured in Coincidence with High-Momentum Protons
R. Sekiya, K. Itahashi, Y. K. Tanaka, S. Hirenzaki, N. Ikeno, V. Metag, M. Nanova, J. Yamagata-Sekihara, V. Drozd et al. (-PRiME Collaboration and Super-FRS Experiment Collaboration)
Physical Review Letters Published: 7 April, 2026
DOI: https://doi.org/10.1103/6vsl-ng7x
Abstract
The missing mass of the 12C(p,d) reaction has been measured near the η′-meson emission threshold in coincidence with a high-momentum proton to selectively collect η′−11C mesic nucleus formation events at GSI, Germany. A 2.5 GeV proton excites a carbon nucleus in order to form an η′-mesic nucleus emitting a deuteron forward with an energy of ∼1.5 GeV. The deuteron is momentum analyzed by the fragment separator used as a high-resolution spectrometer to deduce the excitation energy of the residual system. The large-acceptance detector WASA surrounding the target identifies high-momentum protons emitted in the decay of the η′-mesic nucleus. The measured semiexclusive spectrum exhibits structures below the threshold though the statistical significance is limited. The spectrum is fitted by theoretically calculated spectra varying optical-potential parameters of the η′-nucleus interaction. The analysis results indicate possible formation of η′-mesic nuclei for the real potential depth of ∼−61 MeV with a local statistical significance of 3.5 and, taking into account the look-elsewhere effect, a global significance of 2.1.
