Speaker
Description
On behalf of ACCULINNA collaboration.
The novel results concerning quite “problematic” lightest neutron-rich systems $^4$n [1], $^6$H [2], and $^7$H [3,4] were obtained at ACCULINNA-2 facility (FLNR, JINR, Russia) in the recent years. These experiments provide evidence for very low-energy structures in the spectrum of $^7$H (~2.2 and ~5.5 MeV) and $^4$n (~3.2-3.5 MeV). The latter observation is consistent within experimental uncertainly with the recent observation [5] of the low-energy “resonance-like structure” in the spectrum of $^4$n at ~2.4 MeV.
The existing experimental data on $^4$n, $^6$H, and $^7$H systems is highly controversial and also very complicated to reconsile with theoretical predictions [6,7,8]. We discuss the studies of the $^8$He and $^7$H in a five-body core+4n and of $^4$n in four-body hyperspherical model calculations [1] and their relevance to experimental observations. Some problematic issues about interpretation the data may be resolved in extreme-peripheral reaction scenarious.
The prospects of further experimental studies of $^4$n, $^6$H, and $^7$H systems and requirements to these experiments are discussed. Among other opportunities here we should note the possibility to search for long-living $^7$H states (with width less than something like 1 MeV) in the products of triple fission of heavy nuclei [9].
[1] I.A. Muzalevskii et al., Phys. Rev. C 111 (2025) 014612.
[2] E.Yu. Nikolskii et al., Phys. Rev. C 105 (2022) 064605.
[3] A.A. Bezbakh et al., Phys. Rev. Lett. 124 (2020) 022502.
[4] I.A. Muzalevskii et al., Phys. Rev. C 103 (2021) 044313.
[5] M. Duer et al., Nature 606 (2022) 678.
[6] F. M. Marques and J. Carbonell, The European Physical Journal A 57 (2021) 105.
[7] E. Hiyama, R. Lazauskas, J. Carbonell, Phys. Lett. B 833 (2022) 137367.
[8] H.H. Li, J.G. Li, N. Michel, and W. Zuo, Phys. Rev. C 104 (2021) L061306.
[9] Yu.L. Parfenova et al., in preparation (2025).
