Medium effects to the N(1535) resonance and eta mesic nuclei

The structure of eta-nucleus bound systems (eta mesic nuclei) is investigated as one of the tools to study in-medium properties of the N(1535) (N*) resonance. We show that, as a general consequence, the eta-nucleus potential has a repulsive core at the nuclear center with an attractive part at the nuclear surface, if sufficient reduction of the mass difference of N and N* stems from the in-medium effects to N*. The (d,3He) spectra are evaluated for the formation of these bound states to investigate the experimental feasibility.