Speaker
Description
Spectroscopy of hadronic atoms, where a negatively charged hadron such as π −, K−, or ̄p replaces an electron, offers a unique way to study the strong interaction. Among them, x-ray spectroscopy of antiprotonic atoms provides in-formation on antinucleon–nucleus interactions at low energy. Although a model exists based on global fits to data acquired up to the 1980s, it is limited by uncertainties in nucleon distributions in nuclei [1]. We propose new measurements using calcium isotopes, for which nucleon densities are well known, to reduce these uncertainties. Superconducting microcalorimeter transition-edge sensors offer a resolution of 50–70 eV, which will allow us to determine strong-interaction shifts and widths with an order-of-magnitude improvement over previous studies [2]. The results will refine antinucleon–nucleus optical potential models and have implications for future experiments searching for neutron–antineutron os-
cillations [3, 4].
In this contribution the background of the research will be described, and the status of the recent test experiments will be reported.
References
[1] E. Friedman and A. Gal, Nucl. Phys. A 761, 283 (2005).
[2] T. Higuchi and H. Fujioka, PoS, 480 (EXA-LEAP2024), 049 (2025).
[3] V.V. Nesvizhevsky et al., Phys. Rev. Lett. 122, 221802 (2019).
[4] H. Fujioka and T. Higuchi, arXiv: 2508.17725
