Status of the Search for $$\eta $$-Mesic Nuclei with Particular Focus on $$\eta $$-Helium Bound States

Skurzok, M.

doi:10.1007/s00601-020-01585-x

Cited by 4 publications

(4 citation statements)

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“…In more recent experiments, the search for hypothetical η-bound states in helium nuclei has been carried out employing the Wide Angle Shower Apparatus (WASA) [96] at the COSY accelerator. Three high-statistics, exclusive measurements were performed in 2008, 2010, and 2014, using a deuteron pellet target and deuteron and proton beams to study the possible formation of 4 He-η and 3 Heη bound states, respectively [97]. During each experiment, data were collected as the beam was slowly and continuously accelerated in each cycle, crossing the kinematic threshold for the production of the η meson (corresponding to the η-helium excess energy range Q ∈ (−70, 30) MeV).…”

Section: Search For η-Mesic Helium With Wasa-at-cosy Detectormentioning

confidence: 99%

Search for η-mesic nuclei: a review of experimental and theoretical advances

2023

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In the mid-1980s, theoreticians predicted possible exotic states of an eta (η) meson and a nucleus bound by the strong interaction, so-called mesic nucleus. This led to extensive experimental efforts aimed at discovering such unstable states as well as understanding the underlying interactions via η meson production reactions. As experiments yielded new data, more and more sophisticated theoretical models were developed to understand the fundamental η-nucleon and η-nucleus interactions. After more than 35 years of research in this field, several signals have been identified as possible indications of hypothetical η-mesic nuclei, but there is still no general agreement or clear confirmation of their existence. In the paper, we review the study of the η-mesic nuclei with an emphasis on recent research activities.

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Section: Search For η-Mesic Helium With Wasa-at-cosy Detectormentioning

confidence: 99%

Search for η-mesic nuclei: a review of experimental and theoretical advances

2023

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“…4. As the result of the performed exper- [123,124,125], and are taken from [126]. With kind permission of Springer.…”

Section: The η -Nucleus Interaction and The Search For η Mesic Statesmentioning

confidence: 99%

“…In the model [128], the Green's function technique is used to sum up all η-4 He final states for the estimation of the fusion and η meson production processes. The results compared to the experimentally determined excitation functions resulted in the determination of the exclusion region of (V 0 ,W 0 ) parameters [126,129] which is presented in Fig. 7.…”

Section: The η -Nucleus Interaction and The Search For η Mesic Statesmentioning

confidence: 99%

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The $η$- and $η'$-nucleus interactions and the search for $η$, $η'$- mesic states

Bass¹,

Metag²,

Moskal³

2021

Preprint

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The isoscalar η and η mesons are special in QCD, being linked both to chiral symmetry and to non-perturbative glue associated with the axial anomaly. The properties of these mesons in medium are sensitive to how these dynamics work in the nuclear environment. In contrast to pionic and kaonic atoms which are mainly bound by the Coulomb interaction with some corrections due to the strong force (Coulomb assisted binding), the η and η as neutral mesons can only be bound by the strong interaction. Is this interaction strong enough? This topic has inspired a vigorous program of experiments, conducted in close contact with theory, One has to determine the complex η, η -nucleus potential. Does the real part V provide a sufficiently deep potential? Is the imaginary part W small enough to allow for narrow states that can more easily be detected experimentally, i.e. |W | |V |? The η effective mass is observed to be suppressed by ≈ −40 MeV at nuclear matter density. Bound state searches are ongoing. This article gives an overview of the status of knowledge in this field together with an outlook to future experiments.

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