Quasibound states of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>η</mml:mi></mml:math>-nucleus systems

Rakityansky, S. A.; Sofianos, S. A.; Braun, Moritz; Belyaev, V.B.; Sandhas, W.

doi:10.1103/physrevc.53.r2043

Cited by 69 publications

(79 citation statements)

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“…[44], [45], [14] bound states in light nuclei were calculated by the finite rank approximation (FRA). Within this approximation the motion of the η and of the nucleons inside the nucleus are treated separately.…”

Section: The η Nucleus Potential and Search For Quasi Bound Statesmentioning

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: The η Nucleus Potential and Search For Quasi Bound Statesmentioning

confidence: 99%

Search for quasi boundηmesons

Machner

2015

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

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“…Recently, in a number of theoretical investigations based on quite different approaches, such as the mean field approximation [5], the optical model [6], and few-body calculations [7,8], the idea of η-nuclei was given a rather firm ground. Experimentally, after the discouraging attempt of Ref.…”

Section: Introductionmentioning

confidence: 99%

“…A necessary condition for the existence of η-nuclei, hence, appears to be satisfied. A further indication is the observation of pionic nuclei (deeply bound pion states inside nuclei) [3], which were predicted theoretically in [4].Recently, in a number of theoretical investigations based on quite different approaches, such as the mean field approximation [5], the optical model [6], and few-body calculations [7,8], the idea of η-nuclei was given a rather firm ground. Experimentally, after the discouraging attempt of Ref.…”

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confidence: 99%

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Low-energy ηd-resonance

et al. 2000

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Elastic ηd scattering is considered within the Alt-Grassberger-Sandhas (AGS) formalism for various ηN input data. A three-body resonant state is found close to the ηd threshold. This resonance is sustained for different choices of the two-body ηN scattering length a ηN . The position of the resonance moves towards the ηd threshold when Re a ηN is increased, and turns into a quasi-bound state at Re a ηN = 0.733 fm.PACS numbers: 25.80.-e, 21.45.+v, 25.10.+s One of the main questions of η-meson physics concerns the existence of η-nuclei, a possibility predicted in a pioneering work by Haider and Liu [1]. In this context it is worth mentioning that according to [2] the mean free path of η mesons in a nuclear medium is about 2 fm, i.e., less than the size of a typical nucleus. A necessary condition for the existence of η-nuclei, hence, appears to be satisfied. A further indication is the observation of pionic nuclei (deeply bound pion states inside nuclei) [3], which were predicted theoretically in [4].Recently, in a number of theoretical investigations based on quite different approaches, such as the mean field approximation [5], the optical model [6], and few-body calculations [7,8], the idea of η-nuclei was given a rather firm ground. Experimentally, after the discouraging attempt of Ref. [9], certain evidence for the existence of η-nuclei was noticed by two groups [10,11]. An additional indication is given by the enhancement of near-threshold η production in the reaction np → dη as reported by the Uppsala group [12]. This observation is most likely to be understood as the effect of a near-threshold bound or resonant ηd state. Moreover, it was suggested [13] that even quite exotic systems containing an η meson and a hyperon (η-hypernuclei) may exist.Being of interest by itself, the existence of η-nuclei would also shed new light on various fundamental problems of particle physics. For example, the study of η-nuclei would give a clue for understanding the possible restoration of chiral symmetry in a nuclear medium, or its partial restoration which may occur at normal densities ∼ 0.17 fm −3 [14][15][16]. A further aspect, which makes such systems interesting for other fields of nuclear physics, is the modification of the two-body ηN force by the nuclear medium. Being enhanced due to the resonant character of the ηN interaction, general properties of such modifications should become particularly evident in this case. Especially, the structure of the S 11 resonance embedded in a nuclear medium may be studied. This would exhibit certain details of the effective Lagrangian models of such a resonance [17], and shed some light, for example, on 1 chiral models which suggest a reduction of its partial width for decaying into the ηN channel [16], or assume S 11 to be a quasi-bound state of the K meson and a Σ hyperon [18]. The interesting suggestion of considering S 11 as a joint manifestation of threshold (casp) and resonance phenomena [19] could also be checked.In a sense, the problem of choosing the most adequa...

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“…Parameters of the quasi-bound state were estimated [4,5] from fit to the data. Microscopic four-body calculations support quasi-bound [7] or anti-bound (virtual) [8] states in the 3 He − η system within the existing uncertainties for the elementary ηN interaction. A special type of experiments is required to decide whether the pole in the 3 He − η system, if it really exists, corresponds to a quasi-bound (for strong enough ηN interaction) or anti-bound (for rather weak ηN interaction) state [9].…”

Section: Introductionmentioning

confidence: 61%

Quasi-Bound³He −ηState and Spin-Observables of the Reactionpd→³Heη

Uzikov

2010

EPJ Web of Conferences

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Abstract.A formalism for total set of spin observables of the reaction pd → 3 Heη derived in a model independent way is presented and a possibility to perform a complete polarization experiment is investigated. Separation of s-and p-wave amplitudes of this reaction in the threshold region allows one to determine a position of the quasibound pole in the 3 He − η system. It is shown that in order to get such a separation one should measure spin-transfer coefficients in addition to analyzing powers and spin-correlations. Specific observables, given by products of one s-and one p-wave amplitudes, are found. Measurement of these observables will provide new independent information on the 3 He − η pole position and this allows one to determine whether the 3 He − η state is quasi-bound or anti-bound.

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Quasibound states ofη-nucleus systems

Cited by 69 publications

References 19 publications

Search for quasi boundηmesons

Search for quasi boundηmesons

Low-energy ηd-resonance

Quasi-Bound³He −ηState and Spin-Observables of the Reactionpd→³Heη

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Quasibound states ofη-nucleus systems

Cited by 69 publications

References 19 publications

Search for quasi boundηmesons

Search for quasi boundηmesons

Low-energy ηd-resonance

Quasi-Bound3He −ηState and Spin-Observables of the Reactionpd→3Heη

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Quasi-Bound³He −ηState and Spin-Observables of the Reactionpd→³Heη