The NUMEN Project @ LNS: Status and perspectives

The NUMEN project aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. Particular attention is given to the (18O,18Ne) and (20Ne,20O) reactions as tools for β+β+ and β−β− decays, respectively. First evidence about the possibility to get quantitative information about NME from experiments is found for both kind of reactions. In the experiments, performed at INFN - Laboratory Nazionali del Sud (LNS) in Catania, the beams are accelerated by the Superconducting Cyclotron (CS) and the reaction products are detected by the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to increase the experimental yield of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest. Frontiers technologies are going to be developed, to this purpose, for the accelerator and the detection systems. In parallel, advanced theoretical models will be developed in order to extract the nuclear structure information from the measured cross sections

Recent results on heavy-ion direct reactions of interest for 0νββ decay at INFN - LNS

Neutrinoless double beta decay of nuclei, if observed, would have important implications on fundamental physics. In particular it would give access to the effective neutrino mass. In order to extract such information from 0νββ decay half-life measurements, the knowledge of the Nuclear Matrix Elements (NME) is of utmost importance. In this context the NUMEN and the NURE projects aim to extract information on the NME by measuring cross sections of Double Charge Exchange reactions in selected systems which are expected to spontaneously decay via 0νββ. In this work an overview of the experimental challenges that NUMEN is facing in order to perform the experiments with accelerated beams and the research and development activity for the planned upgrade of the INFN-LNS facilities is reported.Consejo Europeo de Investigación (ERC), Fondo Europeo Programa de investigación e innovación Horizonte 2020 de la Unión n.º 714625)

Near- And Sub-barrier Fusion Of The Be7+ Ni58 System

Evaporation proton yields were measured for the fusion of the radioactive proton-rich nucleus Be-7 onto a Ni-58 target at six near-barrier energies. Total fusion cross sections were deduced by using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential, even for energies above the Coulomb barrier. Inelastic couplings can account for the enhancement at the highest energy. Total fusion channels nearly saturate the total reaction cross section in the measured energy region. Comparison with previous results scaled appropriately for Be-7 + (Al-27, U-238) shows good agreement

The NUMEN heavy ion multidetector for a complementary approach to the neutrinoless double beta decay

Neutrinos are so far the most elusive known particles, and in the last decades many sophisticated experiments have been set up in order to clarify several questions about their intrinsic nature, in particular their masses, mass hierarchy, intrinsic nature of Majorana or Dirac particles. Evidence of the Neutrinoless Double-Beta Decay (NDBD) would prove that neutrinos are Majorana particles, thus improving the understanding of the universe itself. Besides the search for several large underground experiments for the direct experimental detection of NDBD, the NUMEN experiment proposes the investigation of a nuclear mechanism strongly linked to this decay: the Double Charge Exchange reactions (DCE). As such reactions share with the NDBD the same initial and final nuclear states, they could shed light on the determination of the Nuclear Matrix Elements (NMEs), which play a relevant role in the decay. The physics of DCE is described elsewhere in this issue, while the focus of this paper will be on the challenging experimental apparatus currently under construction in order to fulfil the requirements of the NUMEN experiment. The overall structure of the technological improvement to the cyclotron, along with the newly developed detection systems required for tracking and identifying the reaction products and their final excitation level are described

The NUMEN heavy ion multidetector for a complementary approach to the neutrinoless double beta decay

Neutrinos are so far the most elusive known particles, and in the last decades many sophisticated experiments have been set up in order to clarify several questions about their intrinsic nature, in particular their masses, mass hierarchy, intrinsic nature of Majorana or Dirac particles. Evidence of the Neutrinoless Double-Beta Decay (NDBD) would prove that neutrinos are Majorana particles, thus improving the understanding of the universe itself. Besides the search for several large underground experiments for the direct experimental detection of NDBD, the NUMEN experiment proposes the investigation of a nuclear mechanism strongly linked to this decay: the Double Charge Exchange reactions (DCE). As such reactions share with the NDBD the same initial and final nuclear states, they could shed light on the determination of the Nuclear Matrix Elements (NMEs), which play a relevant role in the decay. The physics of DCE is described elsewhere in this issue, while the focus of this paper will be on the challenging experimental apparatus currently under construction in order to fulfil the requirements of the NUMEN experiment. The overall structure of the technological improvement to the cyclotron, along with the newly developed detection systems required for tracking and identifying the reaction products and their final excitation level are described

A constrained analysis of the 40Ca(18O,18F)40K direct charge exchange reaction mechanism at 275 Mev

The40 Ca(18 O,18 F)40 K single charge exchange (SCE) reaction is explored at an incident energy of 275 MeV and analyzed consistently by collecting the elastic scattering and inelastic scattering data under the same experimental conditions. Full quantum-mechanical SCE calculations of the direct mechanism are performed by including microscopic nuclear structure inputs and adopting either a bare optical potential or a coupled channel equivalent polarization potential (CCEP) constrained by the elastic and inelastic data. The direct SCE mechanism describes the magnitude and shape of the angular distributions rather well, thus suggesting the suppression of sequential multi-nucleon transfer processes

Recent results on heavy-ion direct reactions of interest for 0νββ decay at INFN LNS

Neutrinoless double beta decay of nuclei, if observed, would have important implications on fundamental physics. In particular it would give access to the effective neutrino mass. In order to extract such information from 0νββ decay half-life measurements, the knowledge of the Nuclear Matrix Elements (NME) is of utmost importance. In this context the NUMEN and the NURE projects aim to extract information on the NME by measuring cross sections of Double Charge Exchange reactions in selected systems which are expected to spontaneously decay via 0νββ. In this work an overview of the experimental challenges that NUMEN is facing in order to perform the experiments with accelerated beams and the research and development activity for the planned upgrade of the INFN-LNS facilities is reported

A focus on selected perspectives of the NUMEN project

The use of double charge exchange reactions is discussed in view of their application to extract information that may be helpful to determinate the nuclear matrix elements entering in the expression of neutrinoless double beta decay half-life. The strategy adopted in the experimental campaigns performed at INFN - Laboratori Nazionali del Sud and in the analysis methods within the NUMEN project is briefly described, emphasizing the advantages of the multi-channel approach to nuclear reaction data analysis. An overview on the research and development activities on the MAGNEX magnetic spectrometer is also given, with a focus on the chosen technological solutions for the focal plane detector which will guarantee the performances at high-rate conditions