Speaker
Description
The study of photo-nuclear reactions is crucial for understanding nuclear structure and astrophysical processes. The PANDORA (Photo-Absorption of Nuclei and Decay Observation for Reactions in Astrophysics) project [1] aims to systematically investigate these reactions in stable nuclei with mass numbers below 60. We use virtual photon exchange through proton scattering at RCNP. The subsequent decay particles and gamma-rays are detected to measure the photo-absorption cross-section and the decay branching ratio for each decay channel, covering the giant dipole resonance.
The primary objective of the PANDORA project is to elucidate the energy loss mechanisms of ultra-high-energy cosmic ray (UHECR) nuclei during intergalactic propagation. UHECRs are observed on Earth up to energies above 1020 eV by large cosmic-ray air-shower observatories such as Pierre Auger and Telescope Array They remain a mystery in terms of origin, acceleration mechanisms, and composition. Recent analyses suggest a heavier mass composition for UHECRs at the highest energies. UHECR nuclei are predicted to lose energy primarily by emitting particles following photo-nuclear excitation by cosmic microwave background photons. Thus, understanding photonuclear reaction cross-sections and decay branching ratios is essential for interpreting the energy and mass evolution of UHECRs.
I will introduce the project, experimental method at RCNP [2] and the preliminary result of the charged particle decay of IVGDR in 27Al.
References
[1] A. Tamii et al., PANDORA White Paper, Euro. Phys. J. A. 59, 208 (2024).
[2] P. von Neumann-Cosel and A. Tamii, Euro. Phys. J. A 55, 110, (2019)