The quest for light multineutron systems

Marqués, F.M.; Carbonell, J.

doi:10.1140/epja/s10050-021-00417-8

Cited by 22 publications

(13 citation statements)

References 129 publications

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“…The system made of two neutrons, the dineutron, is known to be unbound by only about 100 keV. Whether multi-neutron systems can exist as weakly bound states or very short-lived unbound resonant states has been a long-standing question 1 . The next simplest system of three neutrons is less likely to exist owing to the odd number of nucleons and therefore weaker binding; yet, a recent calculation has suggested its existence 5 .…”

Section: Mainmentioning

confidence: 99%

“…To our knowledge, only neutron stars represent near-pure neutron systems, where neutrons are squeezed together by the gravitational force to very high densities. The experimental search for isolated multi-neutron systems has been an ongoing quest for several decades 1 , with a particular focus on the four-neutron system called the tetraneutron, resulting in only a few indications of its existence so far 2 – 4 , leaving the tetraneutron an elusive nuclear system for six decades. Here we report on the observation of a resonance-like structure near threshold in the four-neutron system that is consistent with a quasi-bound tetraneutron state existing for a very short time.…”

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confidence: 99%

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Observation of a correlated free four-neutron system

Duer

Aumann

Gernhäuser

et al. 2022

Nature

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A long-standing question in nuclear physics is whether chargeless nuclear systems can exist. To our knowledge, only neutron stars represent near-pure neutron systems, where neutrons are squeezed together by the gravitational force to very high densities. The experimental search for isolated multi-neutron systems has been an ongoing quest for several decades1, with a particular focus on the four-neutron system called the tetraneutron, resulting in only a few indications of its existence so far2–4, leaving the tetraneutron an elusive nuclear system for six decades. Here we report on the observation of a resonance-like structure near threshold in the four-neutron system that is consistent with a quasi-bound tetraneutron state existing for a very short time. The measured energy and width of this state provide a key benchmark for our understanding of the nuclear force. The use of an experimental approach based on a knockout reaction at large momentum transfer with a radioactive high-energy 8He beam was key.

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Section: Mainmentioning

confidence: 99%

mentioning

confidence: 99%

Observation of a correlated free four-neutron system

Duer

Aumann

Gernhäuser

et al. 2022

Nature

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“…Experimental evidence for such a four-neutron resonance was recently presented in [23], see also Ref. [25] for a current review of the field. We leave this question for future work.…”

Section: Discussionmentioning

confidence: 95%

Three-body resonances in pionless effective field theory

Dietz,

Hammer,

König

et al. 2021

Preprint

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We investigate the appearance of resonances in three-body systems using pionless effective field theory at leading order. The Faddeev equation is analytically continued to the unphysical sheet adjacent to the positive real energy axis using a contour rotation. We consider both, the three-boson system and the three-neutron system. For the former, we calculate the trajectory of Borromean three-body Efimov states turning into resonances as they cross the three-body threshold. For the latter, we find no sign of three-body resonances or virtual states at leading order. This result is validated by exploring the level structure of three-body states in a finite volume approach.

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“…For a complete and detailed review of all the theoretical calculations concerning multineutrons the reader should check Ref. [50], and will find each of the different works in the references therein. In this section, I will only describe the main categories, cite a few relevant publications, and summarize their conclusions.…”

Section: What Do Theories Say?mentioning

confidence: 99%

The extremes of neutron richness

Marqués

2021

Preprint

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A neutron star is pictured as a gigantic nucleus overwhelmed by the number of neutrons, unlike real atomic nuclei, that have a similar number of neutrons and protons. Is this true? What if we could find, or create nuclei without protons? How far can we go in neutron richness? Our common sense tells us that these neutral nuclei should not exist, but if they do they would change our knowledge on neutron stars, on the properties of nuclei in general, and ultimately on the nucleon-nucleon interaction itself, the building block of matter. This huge potential impact has pushed some ambitious nuclear physicists to search for them since the 1960s. The first positive hints appeared only in the XXI century, and nowadays several collaborations are trying to corner these weird objects and give a definite answer to this crucial question. In this review we will go through this fascinating quest, that started with humble experiments and has now reached a stage of ambitious and sophisticated projects, both in experiment and theory.

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The quest for light multineutron systems

Cited by 22 publications

References 129 publications

Observation of a correlated free four-neutron system

Observation of a correlated free four-neutron system

Three-body resonances in pionless effective field theory

The extremes of neutron richness

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