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

TL;DR

This paper investigates how eta mesons interact with nuclear matter, focusing on the effects of the N*(1535) resonance and chiral symmetry restoration, revealing potential resonance and bound states that influence eta production reactions.

Contribution

It introduces a detailed analysis of eta meson properties considering N*(1535) coupling and chiral mass gap changes, highlighting the emergence of resonance and bound states in eta-nucleus systems.

Findings

Resonance state at about 60 MeV energy.

Two eta-nucleus bound states with approximately -80 MeV binding energy.

Strong influence on eta production cross sections in nuclear reactions.

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 (gamma,p) ^11B reaction with eta-meson production.