Speaker
Description
Cluster models of the nuclear structure describe nuclei as aggregates of transient alpha clusters. These models successfully explain several features that are difficult to reproduce within the traditional shell model, particularly in self-conjugate nuclei such as $^8Be$, $^{12}C$, and $^{16}O$. A notable example is the Hoyle state in $^{12}C$, which can be interpreted as a three-alpha cluster configuration and plays a key role in stellar nucleosynthesis through the triple-alpha process [1].
Experimental investigations of α-cluster structures in $^{16}O$ have mainly focused on its ground state and low-lying excited states [2,3], while some studies have been performed at relativistic energies, from a few GeV per nucleon up to collider energies [4,5]. However, the intermediate energy region of a few hundred MeV per nucleon remains unexplored.
The FOOT (FragmentatiOn Of Target) experiment was designed to study nuclear fragmentation processes of light nuclei with energies ranging from about 100 MeV/n to 700 MeV/n, relevant to both particle therapy and space radiation protection [6,7,8]. Therefore, the experiment provides a unique opportunity to investigate cluster signatures in the intermediate energy range.
In this talk, for the first time, the production of $^8 Be$ in its ground state during the fragmentation of $^{16}O$ is studied in the intermediate energy range. The analysis of FOOT data exploits the high angular resolution of nuclear emulsion films, which allows the identification of correlated alpha pairs originating from the decay of $^{8}Be$. Preliminary results on the production cross section will be presented and compared to predictions from nuclear interaction models.
References
[1] Lombardo, I., & Dell’Aquila, D. (2023). Clusters in light nuclei: history and recent developments. La Rivista del Nuovo Cimento, 46(9), 521-618.
[2] Bijker, R., & Iachello, F. (2017). The algebraic cluster model: Structure of 16O. Nuclear Physics A, 957, 154-176.
[3] Epelbaum, E., Krebs, H., Lähde, T. A., Lee, D., Meißner, U. G., & Rupak, G. (2014). Ab initio calculation of the spectrum and structure of O 16. Physical review letters, 112(10), 102501.
[4] Svetlichnyi, A., Savenkov, S., Nepeivoda, R., & Pshenichnov, I. (2023). Clustering in Oxygen Nuclei and Spectator Fragments in 16O–16O Collisions at the LHC. Physics, 5(2), 381-390.
[5] Glagolev, V., Gulamov, K. G., Lipin, V. D., Lutpullaev, S. L., Olimov, K., Olimov, K. K., ... & Yuldashev, B. S. (2001). Fragmentation of relativistic oxygen nuclei in interactions with a proton. The European Physical Journal A-Hadrons and Nuclei, 11(3), 285-296.
[6] Battistoni, G., Toppi, M., & Patera, V. (2021). Measuring the impact of nuclear interaction in particle therapy and in radio protection in space: the FOOT experiment. Frontiers in Physics, 8, 568242.
[7] Galati, G., Boccia, V., Alexandrov, A., Alpat, B., Ambrosi, G., Argirò, S., ... & Montesi, M. C. (2024). Charge identification of fragments produced in 16O beam interactions at 200 MeV/n and 400 MeV/n on C and C2H4 targets. Frontiers in Physics, 11, 1327202.
[8] Ridolfi, R., Toppi, M., Mengarelli, A., Dondi, M., Alexandrov, A., Alpat, B., ... & Villa, M. (2025). Angular differential and elemental fragmentation cross sections of a 400 MeV/nucleon O 16 beam on a graphite target with the FOOT experiment. Physical Review C, 112(1), 014610.