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HK: Fachverband Physik der Hadronen und Kerne

HK 20: Focus Session: QCD@FAIR

HK 20.4: Gruppenbericht

Mittwoch, 18. März 2026, 14:45–15:05, AM 00.014

Spectroscopy of η′-mesic nuclei at GSI and FAIR — •Kenta Itahashi¹ and Yoshiki Tanaka² for the Super-FRS Experiment collaboration — ¹Department of Physics, The University of Osaka, Japan — ²High Energy Nuclear Physics Laboratory, RIKEN, Saitama, Japan

We have conducted experimental search for η′-nuclei, a bound system of an η′-meson and a carbon 11 nucleus, using FRS at GSI as a high-resolution spectrometer. We measured the missing mass of the ¹²C(p,d) reaction near the η′- emission threshold and selected formation events of the η′-mesic nuclei by tagging a high-momentum proton emitted in the two nucleon absorption channel, η′NN → NN, where N denotes a nucleon. The measured excitation spectrum may indicate first experimental observation of the bound systems of an η′ and a ¹¹C nucleus. We deduced the real part of the η′−¹¹C potential to be −61 ± 1 ± 5 MeV with the local and global statistical significance of 3.5 σ and 2.1 σ, respectively. We plan a new experiment to improve the statistical sensitivity and extend the excitation-energy region of the measurement. We make use of a new solenoidal magnet to be transferred from SPring-8, Japan, which has larger geometry and higher magnetic field to achieve better tagging efficiency. We also discuss possibilities to utilize secondary beams such as pions or antiprotons, using the combination of SIS100 and the SuperFRS.

Keywords: eta'; chiral symmetry; axial U(1) symmetry; FAIR