Are there η-helium bound states?

Wycech, S.; Green, Anthony M.; Niskanen, J.A.

doi:10.1103/physrevc.52.544

Cited by 77 publications

(116 citation statements)

References 19 publications

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“…Also decays into the channels γN, πN, ππN and ηN were considered. The major mechanism that generates the imaginary part of a(ηA) is the reaction ηA i → N * (A − 1) → πA f , where N * is the nucleon resonance N * (1535) with a strong coupling to both the η and the pion [4], [17].…”

Section: ηN Scatteringmentioning

confidence: 99%

Search for quasi boundηmesons

Machner

2015

J. Phys. G: Nucl. Part. Phys.

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The search for a quasi bound η meson in atomic nuclei is reviewed. This tentative state is studied theoretically as well as experimentally. The theory starts from elastic η nucleon scattering which is derived from production data within some models. From this interaction the η nucleus interaction is derived. Model calculations predict binding energies and widths of the quasi bound state. Another method is to derive the η nucleus interaction from excitation functions of η production experiments. The s wave interaction is extracted from such data via final state interaction theorem. We give the derivation of s wave amplitudes in partial wave expansion and in helicity amplitudes and their relation to observables. Different experiments extracting the final state interaction are discussed as are production experiments. So far only three experiments give evidence for the existence of the quasi bound state: a pion double charge exchange experiment, an effective mass measurement, and a transfer reaction at recoil free kinematics with observation of the decay of the state.

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Section: ηN Scatteringmentioning

confidence: 99%

Search for quasi boundηmesons

Machner

2015

J. Phys. G: Nucl. Part. Phys.

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“…Initially the η-mesic nuclei were considered to exists for A ≥ 12 only [97] due to the relatively small value of the ηN scattering length estimated in eighties [98]. A decade later, a large values of the η-nucleon scattering length (1 fm) were extracted in some analysis reported in [99] which do not exclude the formation of bound η-nucleus states for such light nuclei as helium [100,101] or even for deuteron [102]. However, so far none of the experiments have confirmed univocally the existence of such a state neither in reactions induced by pions [103], protons [104], deuterons [105][106][107] or photons [93,108].…”

Section: Threshold Production Of the η − 3 H E And η − H E Systems Anmentioning

confidence: 99%

Few-Body Aspects of the Near Threshold Pseudoscalar Meson Production

Moskal

2014

Few-Body Syst

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During the last decade large samples of data have been collected on the production of the groundstate pseudoscalar mesons in collisions of proton or deuteron beam with hydrogen or deuterium target. These measurements have been performed in the vicinity of the kinematical threshold for meson production where only a few partial waves in both initial and final state are expected to contribute to the production process. This simplifies significantly the interpretation of the data, yet still appears to be challenging due to the three or four particle final state systems with a complex hadronic potential. We review experiments and phenomenology of the near threshold production of the ground-state mesons in the few-body final states as for example: nucleus-meson and nucleon-nucleon-meson, and report on the status of the search of the mesic-nuclei (a meson-nucleus bound states). Experimental advantages of measurements close to the kinematical threshold are discussed, and general features of the production mechanism of the η and η mesons in the nucleon-nucleon collisions are presented emphasising results of measurements of spin and isospin dependence of the production cross sections.

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“…In a much earlier work [17], within a Watson-like multiple scattering formalism, the authors tried to simultaneously analyse the p d → 3 He η as well as the d d → 4 He η data in order to investigate the existence of etamesic helium nuclei. With the η-N interaction not being well-known, they studied the existence of such states for various values of the η-N scattering length.…”

Section: η-mentioning

confidence: 99%

Unresolved Issues in the Search for Eta-mesic Nuclei

Kelkar¹

2015

Acta Phys. Pol. B

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Even if the theoretical definition of an unstable state is straightforward, its experimental identification often depends on the method used in the analysis and extraction of data. A good example is the case of eta mesic nuclei where strong hints of their existence led to about three decades of extensive theoretical and experimental searches. Considering the still undecided status of these states and the limitations in the understanding of the eta-nucleon as well as the eta-nucleus interaction, the present article tries to look back at some unresolved problems in the production mechanism and final state interaction of the eta mesons and nuclei. An unconventional perspective which provides a physical insight into the nature of the eta-nucleus interaction is also presented using quantum time concepts.

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Are there η-helium bound states?

Abstract: Using multiple scattering theory the scattering lengths of η mesons on helium nuclei are calculated and checked against final state η interactions from the pd → η 3 He and dd → η 4 He reactions. The existence of an η 4 He quasibound state is indicated.

Cited by 77 publications

References 19 publications

Search for quasi boundηmesons

Search for quasi boundηmesons

Few-Body Aspects of the Near Threshold Pseudoscalar Meson Production

Unresolved Issues in the Search for Eta-mesic Nuclei

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