Two-step description of heavy ion double charge exchange reactions

Jessica I Bellone,Stefano Burrello,Maria Colonna,José-Antonio Lay,Horst Lenske

doi:10.1016/j.physletb.2020.135528

Jessica I Bellone, Stefano Burrello + Show 3 more

Open Access

https://doi.org/10.1016/j.physletb.2020.135528

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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 Ca40(O18,Ne18)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-decay are pointed out.

Highlights

Nuclear double charge exchange (DCE) reactions are of large current interest after it was realized that they give access to a hitherto hardly explored sector of nuclear excitations
The nuclear ingredients are obtained on the basis of the Giessen EDF (GiEDF) approach [25,26] with Hartree Fock Bogolubov (HFB) ground state densities and on top of them charged current Quasiparticle Random Phase (QRPA) calculations
Heavy ion double charge exchange reactions have been investigated with the focus on the reaction dynamics of this special class of two-step reactions

Summary

Introduction

Nuclear double charge exchange (DCE) reactions are of large current interest after it was realized that they give access to a hitherto hardly explored sector of nuclear excitations. It was realized that under appropriate conditions DCE reactions are the perfect tool for spectroscopic nuclear structure investigations [4,5], being of high interest for the nuclear structure aspects underlying exotic weak interaction processes. Single charge exchange (SCE) reactions [6,7,8,9] to higher order processes. We investigate the conditions under which such reactions can be described as a double single charge exchange (DSCE) process, driven by collisional NN interactions, extending our investigations in Refs. We will show that the DCE reaction amplitudes have a striking formal similarity to the NME of 2ν2β decay While the latter are rare events, heavy ion DCE reactions can be studied suitably under well defined laboratory conditions.

General aspects of two-step DCE reactions

The convolution approach

The separation approach

Numerical details

Analogies to double β–decay

Summary and outlook