Probing beta decay matrix elements through heavy ion charge exchange reactions

J I Bellone,J A Lay,H Lenske,M Colonna

doi:10.1088/1742-6596/1056/1/012004

Abstract

To access information on neutrinoless double beta decay (0νββ) nuclear matrix elements, it has been proposed by the NUMEN collaboration to exploit the analogies between double beta decay processes and double charge exchange (DCE) nuclear reactions, looking in particular at the conditions where the corresponding cross section can be factorized into nuclear reaction and nuclear structure terms. DCE reactions can be treated as a convolution of two correlated or uncorrelated single charge exchange (SCE) processes, resembling 0νββ and 2νββ, respectively. Thus it is important to model first SCE processes, to get a deeper insight into the possibility to factorize the corresponding cross section, so one can gain a better understanding of DCE cross section factorization. In this contribution, DCE reactions are discussed in terms of the convolution of two uncorrelated SCE processes, which should allow one to extract information on 2νββ nuclear matrix elements. These theoretical investigations are performed in close synergy with the experimental activity running at INFN-LNS within the NUMEN project.

Highlights

Nowadays neutrinoless double beta decay (0νββ) represents one of the main probes of Physics beyond the Standard Model, because of its sensitivity to Majorana phases, which appears within the neutrino effective mass, m2β
Published under licence by IOP Publishing Ltd be interpreted like a correlated or uncorrelated sequence of two Single Charge Exchange (SCE) nuclear reactions; in the first case it is possible to establish an analogy between 0νββ decay and Double Charge Exchange (DCE) reaction only on a diagrammatic level, while in the second case there is an analogy between the latter process and the weak 2νββ decay, allowed within the Standard Model, which goes far beyond the mere diagrammatic structure, residing in the kind of spin - isospin operators involved in both weak and strong transitions
The results obtained have been compared to that determined relaxing the factorization hypothesis, as shown in figure 1, where Plane Wave Born Approximation (PWBA) calculations have been included in order just to display distortion factor magnitude and to show the changes in diffraction pattern, strongly influenced by the optical potential, both in full Distorted Wave Born Approximation (DWBA) and in the DWBA - factorized cases

Summary

Introduction

Nowadays neutrinoless double beta decay (0νββ) represents one of the main probes of Physics beyond the Standard Model, because of its sensitivity to Majorana phases, which appears within the neutrino effective mass, m2β. Be interpreted like a correlated or uncorrelated sequence of two Single Charge Exchange (SCE) nuclear reactions; in the first case it is possible to establish an analogy between 0νββ decay and DCE reaction only on a diagrammatic level, while in the second case there is an analogy between the latter process and the weak 2νββ decay, allowed within the Standard Model, which goes far beyond the mere diagrammatic structure, residing in the kind of spin - isospin operators involved in both weak and strong transitions.

Cross Section factorization

Double Charge Exchange reaction kernel

Results for Single and Double Charge Exchange Cross Sections

Conclusions and Outlooks