Annual Report 2024

  The RCNP Annual Report summarizing our activities in FY2024 is now available.

  This year, RCNP has continued to push the frontiers of nuclear physics and its interdisciplinary applications through diverse experimental and theoretical research. Below are some highlights of our achievements in FY2024:

One of the most impactful developments was the regular supply of Astatine-211 (211At) for an investigator-initiated clinical trial in targeted alpha therapy at the University of Osaka Hospital. Using the RCNP AVF cyclotron, we achieved stable monthly production of ^211At, enabling the delivery of therapeutic doses for castration-resistant prostate cancer treatment. The annual beam time dedicated to 211At production reached 840 hours, demonstrating RCNP’s commitment to translational research bridging nuclear physics and medicine.

In the ONOKORO project, we advanced our understanding of cluster formation mechanisms in nuclei by conducting systematic (p, pα) and (p, pX) knockout experiments on calcium and lead isotopes. The observed correlations between α-cluster knockout reactions and neutron excess provide crucial insights into surface clustering phenomena and nuclear dynamics beyond the mean-field approximation.

In collaboration with the J-PARC E31 project, we measured πΣ invariant mass spectra from the d(K−, N)πΣ reactions to elucidate the structure of the Λ(1405) resonance. These results support the two-pole structure of Λ(1405) and provide new constraints on the K̄N scattering amplitudes, reinforcing the interpretation of Λ(1405) as a dynamically generated state.

At LEPS2, a 266 nm pulse laser was successfully installed and operated, enabling photon beam energies up to 2.9 GeV. This upgrade significantly expands the experimental capabilities for polarization-sensitive studies of hadronic structure and exotic meson production.

Another remarkable result was the identification of candidate toroidal electric dipole states in 58Ni through a coordinated analysis of (p, p′), (e, e′), and (γ, γ′) data. These findings suggest the experimental realization of quantized vortical modes in nuclear matter, a long-sought prediction of nuclear theory.

In theoretical studies, we explored the gauge dependence of the charmonium (c c_bar) potential using the HAL QCD method. Comparing Coulomb and Landau gauges, we clarified how gauge choice affects the extracted charm quark mass and interquark potential, offering insights for future studies of diquark dynamics.

Finally, we investigated the role of effective nucleon mass on the thermodynamics of hot nuclear matter. By applying the KIDS density functional theory, we quantified how variations in effective mass influence entropy and the mass–radius relation of proto-neutron stars, with implications for astrophysical modeling.

These highlights represent just a fraction of the innovative research led by RCNP members and our international collaborators. We look forward to the discoveries and developments that lie ahead, as we continue to foster excellence in nuclear science and its applications.

Sincerely yours,

Takashi Nakano
Director of Research Center for Nuclear Physics