Two-step description of heavy ion double charge exchange reactions

Abstract

Heavy ion double charge exchange reactions are described by sequential meson-exchange, corresponding to a double single charge exchange (DSCE) reaction mechanism. The theoretical formulation is discussed. The fully quantum mechanical distorted wave 2-step calculations are shown to be reproduced very well by approximating the intermediate propagator by its pole part. The role of ion-ion elastic interactions is discussed. As a first application, calculations are performed for the reaction 40Ca(18O, 18Ne)40Ar at 15 AMeV. Results are compared to the data measured at LNS by the NUMEN Collaboration. Formal analogies between the nuclear matrix elements (NME) involved in DSCE reactions and in double β-decayare pointed out