Production of $\eta$ and ${\eta }^{\prime }$ Mesons on Nucleons and Nuclei

Abstract

The production of $\eta$ and ${\eta }^{\prime }$ mesons in photon- and hadron-induced reactions on free and quasi-free nucleons and on nuclei is reviewed. The extensive database on $\gamma N\to \eta N$, for both proton and neutron targets, is described in detail and its implications for the search for $N^{\star }$ resonances much heavier than the dominant $S_{11}(1535)$ discussed. Though less is currently known about the production of the ${\eta }^{\prime }$ or of $\eta \pi$ pairs, these also offer tantalizing prospects in the search for the missing isobars. The more limited data available on pion-induced production are still necessary ingredients in the partial wave analysis discussed. The production of the $\eta$-meson in $pp$ and $pn$ collisions shows once again the strong influence of the $S_{11}(1535)$ isobar, which is in contrast to the relatively weak behaviour seen near threshold for ${\eta }^{\prime }$ production. This difference is reflected in the important final state interaction effects of the $\eta$ in nuclei that may even lead to this meson being "bound" in some systems. The evidence for this is reviewed for both $\gamma A$ and $pA$ collisions. The inclusive photoproduction of $\eta$, ${\eta }^{\prime }$, and $\eta \pi$ pairs from nuclei provides further information regarding the production mechanism and the interaction of the $\eta$ and ${\eta }^{\prime }$ with nuclei and the $\eta \pi$ pairs may even allow access to low mass $\eta A$ systems that are forbidden in direct single-meson photoproduction.

accepted for publication in Progress in Particle and Nuclear Physics

Cited by in corpus (12)

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• Search for eta-mesic 4He in the dd->3He n pi0 and dd->3He p pi- reactions with the WASA-at-COSY facility
• Onset of $\eta$-meson binding in the He isotopes
• Few-body calculations of $\eta$-nuclear quasibound states
• First measurement of the polarization observable $E$ and helicity-dependent cross sections in single ${\pi }^0$ photoproduction from quasi-free nucleons
• Photoproduction ofeta-pi pairs off nucleons and deuterons
• Unresolved issues in the search for eta-mesic nuclei
• Helicity-dependent cross sections for the photoproduction of ${\pi }^0$ pairs from nucleons
• Search for eta-mesic nuclei with WASA-at-COSY
• Spin dependence of η meson production in proton-proton collisions close to threshold
• Formation of eta'(958) Meson Bound States by the 6Li(gamma,d) reaction