Eta meson rescattering effects in the [formula omitted] reaction near threshold

Abstract

The p + Li 6 → η + Be 7 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 p + d [ α ] → He 3 [ α ] + η 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–3 N and η–4 N 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.