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

D Carbone ,D Lo Presti,D Bongiovanni,C Agodi,S Tudisco,G Lanzalone,D Calvo,A Foti,D Torresi ,F Longhitano ,F Cappuzzello ,I Boztosun ,J R B Oliveira ,A Spatafora ,A Pakou ,R Linares ,N Deshmukh ,G Russo ,O Sgouros ,F Delaunay ,G A Souliotis ,N H Medina ,A Hacisalihoglu ,A Muoio ,E.r Chávez Lomelí ,M Fisichella ,L Acosta ,Aydın Yıldırım ,Salvatore Calabrese ,M Cavallaro ,G Santagati ,G Gallo ,V Soukeras ,S O Solakcı ,F Iazzi ,F Pinna ,P Finocchiaro ,S Reito ,D Bonanno ,L Pandola ,R Introzzi ,V A B Zagatto

doi:10.1051/epjconf/201819402001

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 (18O, 18Ne) and (20Ne, 20O) 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

The neutrinoless double beta (0νββ) decay is widely searched in many facilities all over the world because its observation would have fundamental implications
The 0νββ decay rate is factorized in three independent factors: the phase-space factor, the Nuclear Matrix Element (NME) and a term that
The precise knowledge of NMEs is necessary to extract information on the neutrino masses, when the decay rate will be possibly measured, and to convert the actual limits on the half-life established by the experiments with different isotopes into limits on the neutrino mass

Summary

Introduction

The neutrinoless double beta (0νββ) decay is widely searched in many facilities all over the world because its observation would have fundamental implications It would establish the Majorana nature of neutrino and has the potential to shed light on the absolute neutrino mass and hierarchy. In order to obtain experimentally driven information on the NMEs, the NUMEN [5] and the NURE [6,7] projects propose to study Heavy-Ion induced Double Charge Exchange (HIDCE) reactions. These reactions are characterized by the transfer of two charge units, leaving the mass number unchanged, and can proceed by a sequential nucleon transfer mechanism or by meson exchange. The (20Ne, 20O) DCE reactions at 15 A∙MeV on 116Cd, 76Ge and 130Te, were recently measured for the first time

The project

The experiments

The data reduction