Search for Quasi Bound $\eta$ Mesons

Abstract

The search for a quasi bound $\eta$ meson in atomic nuclei is reviewed. This tentative state is studied theoretically as well as experimentally. The theory starts from elastic $\eta$ nucleon scattering which is derived from production data within some models. From this interaction the $\eta$ nucleus interaction is derived. Model calculations predict binding energies and widths of the quasi bound state. Another method is to derive the $\eta$ nucleus interaction from excitation functions of $\eta$ 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.

52 figures topical review accepted by Journal of Physics G

References in corpus (68)

• ππscattering
• Three-Body Interactions Among Nucleons and Pions
• Three-body forces: From cold atoms to nuclei
• SU(3) Chiral Dynamics with Coupled Channels: Eta and Kaon Photoproduction
• Chiral Dynamics and the $S_{11}(1535)$ Nucleon Resonance
• Meson production in nucleon--nucleon collisions close to the threshold
• Particle Scale Dynamics in Granular Impact
• Hadrons in strongly interacting matter
• Charmed Mesic Nuclei: Bound D and $\bar{D}$ states with ^{208}Pb
• A QCD Calculation of the Interaction of Quarkonium with Nuclei
• A unitary model for meson-nucleon scattering
• Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV II: photon-induced results
• The $\eta$NN Coupling in Eta Photoproduction
• Photoproduction of eta-mesic 3He
• Chiral dynamics of the S11(1535) and S11(1650) resonances revisited
• Precision study of the eta-3He system using the d+p->3He+eta reaction
• Near-Threshold Production of $\eta$-Mesons
• Measurement of the dp -->3He eta reaction near threshold
• Eta-Helium Quasi-Bound States
• Coherent photoproduction of eta-mesons off 3He - search for eta-mesic nuclei
• eta in the nuclear medium within a chiral unitary approach
• The Eta-Nucleon Scattering Length and Effective Range
• $\eta$ bound states in nuclei
• Is there an eta-3He quasi--bound state ?
• eta-Nucleon Scattering Length and Effective Range uncertainties
• Nuclear bound states of $\omega$ mesons
• Formation of $\eta$-mesic Nuclei Using the Recoilless (d,${}^3$He) Reaction
• Feasibility Study of Observing eta' Mesic Nuclei with (p,d) Reaction
• Eta-nuclear bound states revisited
• In medium eta' mass and eta' N interaction based on chiral effective theory
• Search for the eta-mesic 4He with WASA-at-COSY detector
• Are there eta-Helium bound states?
• Medium effects to N(1535) resonance and eta mesic nuclei
• Pion photoproduction off the proton in a gauge-invariant chiral unitary framework
• Interaction of eta mesons with nuclei
• Dependence of calculated binding energies and widths of $\eta$-mesic nuclei on treatment of subthreshold $\eta$-nucleon interaction
• Near threshold eta meson production in the d+d->alpha+eta reaction
• Recent studies of kaonic atoms and nuclear clusters
• Low-energy etaN interactions: scattering lengths and resonance parameters
• A coupled K-matrix description of the reactions pi+N -> pi+N, pi+N -> eta+N, gamma+N -> pi+N and gamma+N -> eta+N
• Measurement of p + d -> 3He + eta in S(11) Resonance
• Formation of eta-mesic nuclei by (pi,N) reaction and N^*(1535) in medium
• Exclusive measurement of coherent eta photoproduction from the deuteron
• Scattering of vector mesons off nucleons
• Cross Section and Tensor Analysing Power of the $\vec{d}d\to \eta \alpha$ Reaction Near Threshold
• Proton-Proton Spin Correlations at Charm Threshold and Quarkonium Bound to Nuclei
• Study of Omega, Eta, Eta-prime and D-minus mesic nuclei
• Eta and eta-prime meson production in the reaction pn -> dM near threshold
• Absence of spin dependence in the final state interaction of the d(pol) p --> 3He eta reaction
• eta-meson photoproduction off protons and deuterons
• The $\eta$-3N problem with separable interactions
• Bounds on the bound η^3He system
• Coherent photoproduction of pi^0- and eta-mesons off 7Li
• Comment on 'Photoproduction of $\eta$--Mesic ${}^3$He'
• Binding of charmonium with two- and three-body nuclei
• Study of the $\mathbf{p}{+}^6$Li$\to \mathbf{\eta }{+}^7$Be reaction 11.3 MeV above threshold
• Experimental approaches for determining in-medium properties of hadrons from photo-nuclear reactions
• The $\eta {-}^3$He scattering length revisited
• Possible eta-mesic 3He states within the finite rank approximation
• Small eta-N scattering lengths favour eta-d and eta-alpha states
• Low-energy eta-d resonance
• Interference and nuclear medium effects on the eta-mesic nuclear spectrum
• A large acceptance scintillator detector with wavelength shifting fibre read-out for search of eta-nucleus bound states
• Eta meson rescattering effects in the p + 6Li --> eta + 7Be reaction near threshold
• Precision measurements of the pp\to π^+pn and pp\to π^+d reactions: importance of long-range and tensor force effects
• eta-^4He Bound States in the Skyrme Model
• Spin observables of the reaction pd-3He eta and quasi-bound 3He-eta pole
• Binding vs. scattering length: $\eta$ in light nuclei

Cited by in corpus (19)

• Meson-nucleus potentials and the search for meson-nucleus bound states
• Measurement of excitation spectra in the ${}^{12}$C$(p,d)$ reaction near the ${\eta }^{\prime }$ emission threshold
• Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
• Eta-mesic nuclei: past, present, future
• Constraining the optical potential in the search for eta-mesic 4He
• Solution of the eta-4He problem with quasi-particle formalism
• Momentum distribution of N${}^{\ast }$ in nuclei
• Resonance-like structure near the $\eta d$ threshold in the $\gamma d${$\to$}${\pi }^0\eta d$ reaction
• Eta-nuclear interaction: optical vs. coupled channels
• Status and Perspectives of the Search for Eta-Mesic Nuclei
• Luminosity determination for the proton-deuteron reaction using pd -> 3He eta channel with WASA-at-COSY detector
• Systematic few-body analysis of eta-d, eta-3He and eta-4He interaction at low energies
• Theoretical study of the $\gamma d\to {\pi }^0\eta d$ reaction
• Search for the eta-mesic Helium bound state with the WASA-at-COSY facility
• Status of the search for $\eta$-mesic nuclei with particular focus on $\eta$-Helium bound states
• Formation of eta'(958) Meson Bound States by the 6Li(gamma,d) reaction
• $\eta$ bound state: theory and experiment
• Production and interaction of the eta meson with nucleons and nuclei
• Spectator isobar production in the $A\left(\gamma ,\pi NN\right)B$ reaction