Sequential Heavy Ion Double Charge Exchange Reactions and the Link to Double ${\hat{I}}^2$-decay

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 ${}^{40}$Ca ${(}^{18}$O ${,}^{18}$Ne ${)}^{40}$Ar at 15 AMeV. Results are compared to the data measured at LNS by the NUMEN Collaboration. The common aspects of DSCE reactions and double ${\hat{I}}^2$- decay are discussed by a detailed comparison of the respective nuclear matrix elements (NME).

submitted to Phys. Lett. B