The possible existence of eta-nucleus bound states has been put forward through theoretical and experimental studies. It is strongly related to the eta mass at finite density, which is expected to be reduced because of the interplay between the $U_A(
1)$ anomaly and partial restoration of chiral symmetry. The investigation of the C(p,d) reaction at GSI and FAIR, as well as an overview of the experimental program at GSI and future plans at FAIR are discussed.
The mass of the {eta} meson is theoretically expected to be reduced at finite density, which indicates the existence of {eta}-nucleus bound states. To investigate these states, we perform missing-mass spectroscopy for the (p, d) reaction near the {et
a} production threshold. The overview of the experimental situation is given and the current status is discussed.
