1 A rigorous study of the η - nucleus interaction in the p d → 3 He η reaction near threshold

A detailed study of the effect of the η-nucleus final state interaction (FSI) in the p d → He η reaction close to threshold is presented. The FSI is incorporated through a T-matrix for η He elastic scattering, constructed using few body equations. This T-matrix accounts for off-shell and binding effects in η-nucleus scattering. The energy dependence of the data on the p d → He η reaction near threshold is reproduced only after including the FSI. The off-shell and binding effects in η He scattering are found to be important. Given the uncertainty in the knowledge of the elementary η-nucleon interaction, the sensitivity of the p d → He η cross section to the ηN scattering length is also discussed. PACs numbers: 13.75.-n, 25.40.Ve, 25.10.+s