Off-shell model for threshold pionic<i>η</i>production on a nucleon and for<i>ηN</i>scattering

Bhalerao, Rajeev S.; Liu, L.C.

doi:10.1103/physrevlett.54.865

Cited by 226 publications

(263 citation statements)

References 8 publications

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“…Contrary to this, the η-nucleon interaction at small momenta is attractive and rather strong. This was first pointed out by Bhalerao and Liu [9] and later applied by Haider and Liu [10] to predict quasi bound η mesons in atomic nuclei for mass numbers A ≥ 12.…”

Section: Introductionmentioning

confidence: 84%

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: Introductionmentioning

confidence: 84%

Search for quasi boundηmesons

Machner

2015

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

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“…We choose the parameter set with g N * = 2.13, β = 13 fm −1 , and M 0 = 1656 MeV which leads to a ηN = (0.88, 0.41) fm. We also present results using one of the earliest calculations of the η-N t-matrix [2] which gives a much smaller value of the scattering length, namely, a ηN = (0.28, 0.19) fm. In this model, the πN, ηN and π∆ (ππN) channels were treated in a coupled channel formalism (so that an additional self-energy term appears in the propagator in Eq.…”

Section: T -Matrix For η-Nucleus Elastic Scatteringmentioning

confidence: 99%

“…The root of the debate lies in the uncertainty in the knowledge of the elementary eta-nucleon (ηN) interaction. Though once again, the first prediction of an attractive ηN interaction [2] (arising basically due to the proximity of the ηN threshold to the N * (1535) resonance) was made back in 1985, an agreement on the magnitude of the attraction has not been reached. Though most of the models are constrained by the same sets of data on πN elastic scattering and the πN → ηN cross sections, the ηN scattering length predicted by different models is very different due to the unavailability of direct experimental information on ηN elastic scattering.…”

Section: Introductionmentioning

confidence: 99%

ηN scattering lengths favour ηd and ηα states

Kelkar

Khemchandani

Jain

2006

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

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Unstable states of the eta meson and the 3 He nucleus predicted using the time delay method were found to be in agreement with a recent claim of η-mesic 3 He states made by the TAPS collaboration. Here, we extend this method to a speculative study of the unstable states occurring in the ηd and η 4 He elastic scattering. The T -matrix for η 4 He scattering is evaluated within the Finite Rank Approximation (FRA) of few body equations. For the evaluation of time delay in the ηd case, we use a parameterization of an existing Faddeev calculation and compare the results with those obtained from FRA. With an ηN scattering length, a ηN = (0.42, 0.34) fm, we find an ηd unstable bound state around −16 MeV, within the Faddeev calculation. A similar state within the FRA is found for a low value of a ηN , namely, a ηN = (0.28, 0.19) fm. The existence of an η 4 He unstable bound state close to threshold is hinted by a ηN = (0.28, 0.19) fm, but is ruled out by large scattering lengths.

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“…This resonance, which is strongly coupled to the ηN and πN channels, lies only ∼ 50 MeV above the ηN threshold and has a very broad width of Γ ≈ 150 MeV [1]. The η-nucleus dynamics, thus, is of interest from the point of view of both few-body and meson-nucleon physics.In the energy region covering the S 11 -resonance, the πN and ηN scattering processes are to be considered as a coupled-channel problem [2][3][4]. The first of these channels has a long record of theoretical and experimental investigations, while the second one is understood only in a rudimentary way.…”

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confidence: 99%

Threshold scattering of the η-meson off light nuclei

et al. 1995

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The scattering lengths of η-meson collisions with light nuclei 2 H, 3 H, 3 He, and 4 He are calculated on the basis of few-body equations in coherent approximation. It is found that the η-nucleus scattering length depends strongly on the number of nucleons and the potential-range parameter. By taking into account the off-shell behavior of the ηN amplitude, the ηα scattering length increases considerably.In η-nucleus collisions at threshold energies, a large Final State Interaction (FSI) is expected due to the N * (1535) S 11 -resonance. This resonance, which is strongly coupled to the ηN and πN channels, lies only ∼ 50 MeV above the ηN threshold and has a very broad width of Γ ≈ 150 MeV [1]. The η-nucleus dynamics, thus, is of interest from the point of view of both few-body and meson-nucleon physics.In the energy region covering the S 11 -resonance, the πN and ηN scattering processes are to be considered as a coupled-channel problem [2][3][4]. The first of these channels has a long record of theoretical and experimental investigations, while the second one is understood only in a rudimentary way. The πN and ηN channels are connected to each other primarily via the N * (1535) resonance. In fact, the ηNN coupling constant was shown to be negligible [5][6][7] as compared to the one of the ηNN * vertex. This latter vertex constant, being hence crucial for determining the ηN interaction, is known only with a large uncertainty, so that the ηN scattering length inferred from it varies from (0.27 + i 0.22)fm [2] to (0.55 + i 0.30)fm [8]. The ηN near-threshold interaction, therefore, remains an interesting field of investigation. Of particular relevance in this context is the possibility of η-nucleus bound states [9,10]. Their existence would provide us with an excellent opportunity to answer the above-mentioned questions in a reliable manner.

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Off-shell model for threshold pionicηproduction on a nucleon and forηNscattering

Cited by 226 publications

References 8 publications

Search for quasi boundηmesons

Search for quasi boundηmesons

ηN scattering lengths favour ηd and ηα states

Threshold scattering of the η-meson off light nuclei

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