Level crossing of particle–hole and mesonic modes in eta-mesonic nuclei

Abstract

We study eta-meson properties in the infinite nuclear matter and in atomic nuclei with an emphasis on effects of the eta coupling to N ∗ ( 1535 ) -nucleon–hole modes. The N ∗ ( 1535 ) resonance, which dominates the low-energy eta-nucleon scattering, can be seen as a chiral partner of the nucleon. The change of the chiral mass gap between the N ∗ and the nucleon in a nuclear medium has an impact on the properties of the eta-nucleus system. If the N ∗ -nucleon mass gap decreases with a density increase (chiral symmetry restoration) the calculations show the existence of the resonance state at the energy about 60 MeV and two bound eta-nucleus states with the binding energies about − 80 MeV . These states can have strong effect on predicted cross sections of the 12C ( γ , p ) 11B reaction with eta-meson production.