Investigating double charge-exchange transitions with nuclear reactions

Collisional heavy-ion double charge exchange (DCE) reactions, arising from second-order nucleon-nucleon interactions, are investigated. These reactions offer a unique avenue for exploring two-body transition densities (2BTD) as­sociated with nuclear DCE processes. The reaction mechanism is treated us­ing a second-order distorted wave formalism, where the intrinsic interaction is expressed in terms of an s-channel two-body operator. We show that this theoretical approach enables a consistent description of complementary DCE transitions, and related 2BTDs, in both projectile and target nuclei. As a repre­sentative case, results are shown for the reaction 18O + 76Se → 18Ne + 76Ge at a laboratory energy of Tlab = 270 MeV. The nucleus 76Ge, being a well-known candidate for neutrinoless double beta decay (DBD), makes this reaction par­ticularly relevant for studies of nuclear matrix elements underpinning such rare processes.