Search for $\eta '$(958)--nucleus Bound States by $(p,d)$ Reaction at GSI and FAIR

The mass of the η′ meson is theoretically expected to be reduced at finite density, which indicates the existence of η′–nucleus bound states. To investigate these states, we perform missing-mass spectroscopy for the (p,d) reaction near the η′ production threshold. The overview of the experimental situation is given and the current status is discussed.