The NUMEN Project: Toward New Experiments with High-Intensity Beams

Luigi Campajola,Domenico Torresi,Manuela Cavallaro,Clementina Agodi,Diego Sartirana,Vittoria Capirossi,Paolo Finocchiaro,Felice Iazzi,Federico Pinna,Grazia D’Agostino,Diana Carbone,Antonio D. Russo,Daniela Calvo,Luciano Calabretta,Luciano Pandola,Francesco Cappuzzello

doi:10.3390/universe7030072

Abstract

The search for neutrinoless double-beta (0νββ) decay is currently a key topic in physics, due to its possible wide implications for nuclear physics, particle physics, and cosmology. The NUMEN project aims to provide experimental information on the nuclear matrix elements (NMEs) that are involved in the expression of 0νββ decay half-life by measuring the cross section of nuclear double-charge exchange (DCE) reactions. NUMEN has already demonstrated the feasibility of measuring these tiny cross sections for some nuclei of interest for the 0νββ using the superconducting cyclotron (CS) and the MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS.) Catania, Italy. However, since the DCE cross sections are very small and need to be measured with high sensitivity, the systematic exploration of all nuclei of interest requires major upgrade of the facility. R&D for technological tools has been completed. The realization of new radiation-tolerant detectors capable of sustaining high rates while preserving the requested resolution and sensitivity is underway, as well as the upgrade of the CS to deliver beams of higher intensity. Strategies to carry out DCE cross-section measurements with high-intensity beams were developed in order to achieve the challenging sensitivity requested to provide experimental constraints to 0νββ NMEs.

Highlights

The strong interest in the double-beta decay processes began in 1939, when Wendell Furry [1], starting from the work of Maria Goeppert-Mayer [2], applied the neutrino model previously proposed by Ettore Majorana [3], in which there is no distinction between particle and antiparticle and which proposes a new hypothetical decay, known as neutrinoless double-beta (0νββ) decay.The 0νββ decay is a hypothetic class of nuclear processes where a parent nucleus is transformed into an isobar daughter differing by two-unit charges and two electrons are emitted
The double-charge exchange (DCE) reaction process needs to be described in detail to identify the relevant nuclear response from the measured DCE cross sections, which is by itself an interesting research goal for nuclear reaction theory
DCE nuclear matrix elements (NMEs) can be inferred by measured cross sections under controlled laboratory conditions and can be connected to NMEs relevant for 0νββ decay [71]

Summary

Introduction

The strong interest in the double-beta decay processes began in 1939, when Wendell Furry [1], starting from the work of Maria Goeppert-Mayer [2], applied the neutrino model previously proposed by Ettore Majorana [3], in which there is no distinction between particle and antiparticle and which proposes a new hypothetical decay, known as neutrinoless double-beta (0νββ) decay. This fact makes the determination of NMEs based on different calculation schemes controversial, given the lack of experimental constraints In this context, the NUMEN project [18,19,20,21] aims to obtain quantitative information on the NMEs of 0νββ decay by measuring heavy ion–DCE reaction cross sections. The NUMEN Holy Grail is to study if the DCE cross section, and the DCE NME, is connected to 0νββ NMEs as a smooth function of incident beam energy and target mass This goal requires the development of the reaction and nuclear structure theory and a systematic set of data. The ratio of the DCE cross section can be regarded as a model independent way to compare the sensitivity of 0νββ decay experiments using different isotopes To achieve these goals, the project promotes a specific R&D activity with the upgrade of the whole INFN-LNS research infrastructure. The NUMEN future phase will consist of a series of experimental campaigns using 18O and 20Ne beams of high intensities (some pμA) and integrated charge of hundreds of mC up to C, for experiments in which coincidence measurements are required, spanning all the variety of 0νββ decay candidate isotopes of interest, like 48Ca, 76Ge, 76Se, 82Se, 96Zr, 100Mo, 106Cd, 110Pd, 116Cd, 110Sn, 124Sn, 128Te, 130Te, 136Xe, 130Xe, 148Nd, 150Nd, 154Sm, 160Gd, and 198Pt

NUMEN Experimental Tools

The NUMEN Upgrade

The NUMEN Particle Accelerator

The New Beam Lines inside the MAGNEX Hall

NUMEN Strategy for Experiments with High-Intensity Beams

Findings

Discussion