The nuclear matrix elements of 0νββdecay and the NUMEN project at INFN-LNS

F Cappuzzello ,G Lanzalone,F Balestra,D Calvo,C Agodi,D Bongiovanni,S Tudisco,D Lo Presti,A Calanna,A Foti,R Bijker ,M.v Ruslan ,A Muoio ,Simone Ferrero ,F Longhitano ,P Finocchiaro ,M Colonna ,E Santopinto ,Salvatore Calabrese ,Vincenzo Branchina ,M Cavallaro ,D Carbone ,Luciano Scaltrito ,V Greco ,D Rifuggiato ,F Iazzi ,D Bonanno ,L Calabretta ,G Giraudo ,L Pandola ,Andrea Lavagno ,R Introzzi ,V A B Zagatto

doi:10.1051/epjconf/201611710003

Abstract

The goal of NUMEN project is to access experimentally driven information on Nuclear Matrix Elements (NME) involved in the neutrinoless double beta decay (0νββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. The knowledge of the nuclear matrix elements is crucial to infer the neutrino average masses from the possible measurement of the half-life of 00νββ decay and to compare experiments on different isotopes. In particular, the (18 O, 18 Ne) and (20 Ne, 20 O) reactions are performed as tools for β+ β+ and β- β- decays, respectively. The experiments are performed at INFN - Laboratory Nazionali del Sud (LNS) in Catania using the Superconducting Cyclotron (CS) to accelerate the beams and the MAGNEX magnetic spectrometer to detect the reaction products. The measured cross sections are very low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. In order to make feasible a systematic study of all the candidate nuclei, a major upgrade of the LNS facility is foreseen to increase the experimental yield of about two orders of magnitude. To this purpose, frontier technologies are going to be developed for both the accelerator and the detection systems. In parallel, advanced theoretical models will be developed to extract the nuclear structure information from the measured cross sections.

Highlights

Neutrinoless double beta decay, 0νββ, is at the present time strongly pursued both experimentally and theoretically [1]
On the basis of the above mentined ground-breaking achievement, we propose an ambitious project, NUMEN, with the aim to go deep inshight in the HI-double charge exchange (DCE) studies on nuclei of interest in 0νββ decay[3]
There are a number of important similarities among DCE and 0νββ decay processes, despite they are mediated by different interactions, the description of Nuclear Matrix Elements (NME) extracted from DCE and 0νββ presents the same degree of complexity, with the advantage for DCE to be accessible in laboratory

Summary

Introduction

Neutrinoless double beta decay, 0νββ, is at the present time strongly pursued both experimentally and theoretically [1]. An innovative technique to access the Nuclear Matrix Elements (NME) entering the expression of the life time of the 0νββ by relevant cross sections of double charge exchange (DCE) reactions is proposed. First pioneering experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, give encouraging indication on the capability of the proposed technique to access relevant quantitative information. First experimental results, obtained at the INFN-LNS laboratory in Catania, for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV, in a wide range of transferred momenta, give encouraging indication on the capability to access quantitative information towards the determination of the NME for 0νββ decay [2]. A simple relation between DCE cross sections and ββ-decay half-lives is not trivial and needs to be explored

The project

The facility upgrade

Perspectives