Eta meson rescattering effects in the reaction near threshold

The reaction has been investigated with an emphasis on the η meson and 7Be interaction in the final state. Considering the 6Li and 7Be nuclei to be α–d and α–3He clusters respectively, the reaction is modelled to proceed via the reaction with the α remaining a spectator. The η meson interacts with 7Be via multiple scatterings on the 3He and α clusters inside 7Be. The individual η–3He and η–α scatterings are evaluated using few body equations for the η–3N and η–4N systems with a coupled channel η–N interaction as an input. Calculations including four low-lying states of 7Be lead to a double hump structure in the total cross section corresponding to the L=1 (J=−(1/2),−(3/2)) and L=3 (J=−(5/2),−(7/2)) angular momentum states. The humps arise due to the off-shell rescattering of the η meson on the 7Be nucleus in the final state.