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Observation of a correlated free four-neutron system

ABSTRACT: 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. Experiment based on knocking out an alpha particle from a high-energy helium isotope shows a resonance-like structure that is consistent with a quasi-bound tetraneutron state existing for a very short time.

SUBMITTER: Duer M

PROVIDER: S-EPMC9217746 | biostudies-literature | 2022 Jan

REPOSITORIES: biostudies-literature

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