Production of η and η′ mesons on nucleons and nuclei

Abstract

The production of η and η mesons in photon-and hadron-induced reactions on free and quasifree nucleons and on nuclei is reviewed. The extensive database on γN → ηN , for both proton and neutron targets, is described in detail and its implications for the search for N resonances much heavier than the dominant S 11 (1535) discussed. Though less is currently known about the production of the η or of ηπ 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 η-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 η production. This difference is reflected in the important final state interaction effects of the η in nuclei that may even lead to this meson being "bound" in some systems. The evidence for this is reviewed for both γA and pA collisions. The inclusive photoproduction of η, η , and ηπ pairs from nuclei provides further information regarding the production mechanism and the interaction of the η and η with nuclei and the ηπ pairs may even allow access to low mass ηA systems that are forbidden in direct single-meson photoproduction.

Study of η and η′ Photoproduction at MAMI

“…A review of the experimental and phenomenological progress can be found in Ref. [7]. All model calculations [8][9][10][11][12][13] agree in the dominance of the E 0þ ðJ P ¼ 1=2 − Þ multipole amplitude, which is populated by the well established Nð1535Þ1=2…”

Constraining the optical potential in the search for η-mesic 4He

“…They provide only signals which might be interpreted as indications of the η-mesic nuclei. The interested reader can find recent reviews on the η mesic bound states searches in Refs [4,5,14,16,39,40,41,42,43,44].…”

Formation of $\eta{^\prime}$ (958) meson bound states by the 6Li( $\gamma$ ,d) reaction

“…In this article, we consider the formation of the η ′ bound states in the α particle in the 6 Li(γ, d ) reaction and report the calculated results of the formation cross section. It should also be noted that the η meson-nucleus systems have been studied for a long time both theoretically and experimentally [10,11,12,13]. This paper is organized as follows.…”