Formal Theory of Heavy Ion Double Charge Exchange Reactions

TL;DR

This paper develops a comprehensive theoretical framework for heavy ion double charge exchange reactions, highlighting their connection to nuclear matrix elements and Majorana neutrino processes, with implications for understanding nuclear structure and neutrino physics.

Contribution

It introduces a detailed theoretical model for DCE reactions, emphasizing the roles of DSCE and MDCE mechanisms, and draws parallels with neutrinoless double beta decay.

Findings

DSCE reactions are second-order distorted wave processes mediated by isovector NN interactions.

Response functions resemble nuclear matrix elements of $2 u 2eta$ decay.

MDCE involves an effective isotensor interaction similar to neutrino potentials.

Abstract

The theory of heavy ion double charge exchange (DCE) reactions $A(Z,N)\to A(Z\pm 2,N\mp 2)$ is recapitulated emphasizing the role of Double Single Charge Exchange (DSCE) and pion-nucleon Majorana DCE (MDCE) reactions. DSCE reactions are of second--order distorted wave character, mediated by isovector nucleon-nucleon (NN) interactions. The DSCE response functions resemble the nuclear matrix elements (NME) of $2\nu 2\beta$ decay. The MDCE process proceeds by a dynamically generated effective rank-2 isotensor interaction, defined by off--shell pion--nucleon DCE scattering. In closure approximation pion potentials and two--nucleon correlations are obtained, similar to the neutrino potentials and the intranuclear exchange of Majorana neutrinos in $0\nu 2 \beta$ Majorana double beta decay (MDBD).