New experimental approaches to determine the real part of the η'-nucleus potential

Transparency ratio measurements provide information on the inelastic cross section and in-medium width of η' and thereby on the imaginary part of the η'-nucleus potential. The real part of the η'-nucleus optical potential can be deduced from the measurement of the η' excitation function and of the η' momentum distribution which are sensitive to the sign and depth of the potential. Data taken in 2009 at CB/TAPS rate at ELSA on a carbon target have been analysed. The results are compared to model calculations assuming different scenarios for the real part of the potential, related directly to the in-medium mass modification of the meson. The data are consistent with a weakly attractive η'-nucleus potential.