Speaker
Description
Studying short-distance production of multi-particle states provides a powerful theoretical approach to investigate high-energy reactions with low-energy final states in nuclear physics, particularly in hard knock-out reactions such as recent and forthcoming multi-neutron experiments [0,1,2,5,6,7,8,9]. Understanding these states requires an accurate, ideally model-independent, description of their production. Short-distance production is essential, as it is independent of initial distributions and allows direct study of the system and its final-state interactions. For this purpose, effective field theory provides a framework for a model-independent treatment of interactions. We apply this short-distance production framework to systems of three and four neutrons to investigate the possible emergence of multi-neutron resonances. As a first step, we demonstrate that short-distance production is indeed capable of signaling a multi-particle resonance in the case of Efimov resonances.
With this benchmark in mind, we then study whether resonance structures appear for three- and four-neutron systems. Consistent with expectations from Schrödinger symmetry [4] and the large charge expansion [11], no resonance-like structure is observed for short-distance production, in agreement with other EFT calculations [10]. However, recent tetraneutron experiments report the observation of a resonance-like structure [2]. As shown by Lazauskas et al. [3], assuming a non-pointlike initial spatial distribution of the four neutrons can lead to a structure compatible with the experimental observations of Duer et al. [2]. To account for this effect, we use our results to obtain final state four-neutron distributions considering some initial neutron distributions. This procedure allows to generate a resonance-like structure.
[0] F. M. Marqués and J. Carbonell, The quest for light multineutron systems, Eur. Phys. J. A 57, 105 (2021).
[1] R. Y. Kezerashvili, Search of trineutron and tetra-neutron, in 6th International Conference on Fission and Properties of Neutron Rich Nuclei (2016).
[2] M. Duer et al., Observation of a correlated free four-neutron system, Nature 606, 678 (2022).
[3] R. Lazauskas, E. Hiyama, and J. Carbonell, Low energy structures in nuclear reactions with 4n in the finalstate, Phys. Rev. Lett. 130, 102501 (2023).
[4] H.-W. Hammer and D. T. Son, Unnuclear physics: Conformal symmetry in nuclear reactions, Proc. Nat. Acad. Sci. 118, e2108716118 (2021).
[5] F. M. Marqués, M. Labiche, A. Orr, N. A., et al., Detection of neutron clusters, Phys. Rev. C 65, 044006 (2002).
[6] K. Kisamori, S. Shimoura, H. Miya, et al., Candidate resonant tetraneutron state populated by the 4He(8He,8Be) reaction, Phys. Rev. Lett. 116, 052501 (2016).
[7] T. Faestermann, A. Bergmaier, R. Gernhäuser, et al., Indications for a bound tetraneutron, Phys. Lett. B 824, 136799 (2022).
[8] K. Miki, K. Kameya, D. Sakai, et al., Precise spectroscopy of the 3n and 3p systems via the 3H(t,3He)3n and 3He(3He,t)3p reactions at intermediate energies, Phys. Rev. Lett. 133, 012501 (2024).
[9] T. Faestermann and R. Gernhäuser, Recent results on the tetraneutron, arXiv preprint:2506.11623 (2025).
[10] S. Zhang, S. Elhatisari, and U.-G. Meißner, Multi-neutron correlations in light nuclei via ab-initio lattice simulations, arXiv:2512.18849 [nucl-th].
[11] S. R. Beane, D. Orlando, and S. Reffert, Unnuclear matter at large charge, Phys. Rev. D 112, 014028 (2025).
| Theoretical or experimental | Theoretical |
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