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.
A novel method is proposed to measure eta(958) meson bound states in 11C nuclei by missing mass spectroscopy of the 12C(p,d) reaction near the eta production threshold. It is shown that peak structures will be observed experimentally in an inclusive
measurement in case that the in-medium eta mass reduction is sufficiently large and that the decay width of eta mesic states is narrow enough. Such a measurement will be feasible with the intense proton beam supplied by the SIS synchrotron at GSI combined with the good energy resolution of the fragment separator FRS.
