Heavy Ion Double Charge Exchange Reactions as Probes for Two-Body Transition Densities

Collisional heavy ion double charge exchange (DCE) reactions, induced by second order nucleon-nucleon interactions, are shown to provide access to the two-body transition densities of the complementary DCE transitions in the interacting nuclei. Corresponding two-body operators are introduced, treating the second order distorted wave reaction amplitude in the s-channel interaction form. The theoretical results are applied to the reaction ${}^{18}O+{}^{76}Se\to {}^{18}Ne+{}^{76}Ge$ at $T_{lab}=270$~MeV, being ${}^{76}Ge$ a candidate for neutrino–less double beta decay.