eta in the nuclear medium within a chiral unitary approach

The self-energy of an eta meson in the nuclear medium is calculated in a chiral unitary approach. A coupled channel Bethe-Salpeter equation is solved to obtain the effective eta-N interaction in the medium. The base model reproduces well the free space pi-N elastic and inelastic scattering at the eta-N threshold or N^*(1535) region. The Pauli blocking on the nucleons, binding potentials for the baryons and self-energies of the mesons are incorporated, including the eta self-energy in a self-consistent way. Our calculation predicts about -54 -i29 MeV for the optical potential at normal nuclear matter for an eta at threshold but also shows a strong energy dependence of the potential.