The exchange of ρ-mesons in π-d and π-4He elastic scattering

A rescattering process for π-deuteron and π?⁴He elastic scattering in which the intermediate state contains a ρ-meson instead of the π-meson is studied in the energy region of the 3,3 pionnucleon resonance. It is found that the contribution of such a process is negligible in the forward direction, but amounts to some 5 % to 10 % (or even more) of the cross sections at large angles. Great sensitivity to the off-shell behavior of the NΔ vertex and to the short-range two-body correlations in the nucleus is found.