Interference and nuclear medium effects on the eta-mesic nuclear spectrum

Abstract

The missing-mass spectrum obtained in a recoil-free transfer reaction p(${}^{27}$Al,${}^3$He)${\pi }^{-}$p'X is analyzed. We find that the observed peak structure arises from the coherent contributions from two reaction processes in the energy region corresponding to a bound eta ($\eta$) meson. In one of the processes the intermediate $\eta$ is captured by the nucleus to form the $\eta$-mesic nucleus ${}^{25}$Mg${}_{\eta }$. In the other process, the $\eta$ does not form $\eta$-nucleus bound state. The interference between these two processes has caused the peak of the spectrum to appear at an $\eta$ binding energy stronger than the actual one. Our analysis also indicates that the data are consistent with an attractive N*(1535)-nucleus interaction at energies below the $\eta$N threshold.

12 pages, 3 figures

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• Eta-nuclear bound states revisited
• Interaction of eta mesons with nuclei
• Search for Quasi Bound $\eta$ Mesons
• Eta-mesic nuclei: past, present, future
• Constraining the optical potential in the search for eta-mesic 4He
• Status and Perspectives of the Search for Eta-Mesic Nuclei
• Status of the search for $\eta$-mesic nuclei with particular focus on $\eta$-Helium bound states
• $\eta$ bound state: theory and experiment