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The MAGNEX magnetic spectrometer is used in the experimental measurements of Double Charge Exchange and Multi-Nucleon Transfer reactions induced by heavy ions within the NUMEN project. These processes are characterized by small cross sections under a large background due to other reaction channels. Therefore an accurate control of the signal to background ratio is mandatory. In this article, the determination of the MAGNEX spectrometer background contribution on cross section measurements is presented by applying a suitable analysis to quantify the limits of the adopted particle identification technique. The method is discussed considering the 116Cd(20Ne, 20O)116Sn Double Charge Exchange reaction data, however it can be applied to any other reaction channel of interest. © 2020 Elsevier B.V.

International audience; Background: Double charge exchange (DCE) nuclear reactions have recently attracted much interest as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-β decay. In this framework, a good description of the reaction mechanism and a complete knowledge of the initial and final-state interactions are mandatory. Presently, not enough is known about the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for future DCE studies. Among these, the Ne20+Ge76 DCE reaction is particularly relevant due to its connection with Ge76 double-β decay. Purpose: We intend to characterize the initial-state interaction for the Ne20+Ge76 reactions at 306 MeV bombarding energy and determine the optical potential and the role of the couplings between elastic channel and inelastic transitions to the first low-lying excited states. Methods: We determine the experimental elastic and inelastic scattering cross-section angular distributions, compare the theoretical predictions by adopting different models of optical potentials with the experimental data, and evaluate the coupling effect through the comparison of the distorted-wave Born approximation calculations with the coupled channels ones. Results: Optical models fail to describe the elastic angular distribution above the grazing angle (≈9.4∘). A correction in the geometry to effectively account for deformation of the involved nuclear systems improves the agreement up to about 14∘. Coupled channels effects are crucial to obtain good agreement at large angles in the elastic scattering cross section. Conclusions: The analysis of elastic and inelastic scattering data turned out to be a powerful tool to explore the initial and final-state interactions in heavy-ion nuclear reactions at high transferred momenta.

New experimental measurements of charge state distributions produced by a 20 Ne 10+ beam at 15 MeV/u colliding on various thin solid targets are presented. The use of the MAGNEX magnetic spectrometer enabled measurements of the 8 + charge state down to fractions of a few 10 −5 . The use of different post-stripper foils located downstream of the main target is explored, showing that low Z materials are particularly effective to shift the charge state distributions towards fully stripped conditions. The dependence on the foil thickness is also studied and discussed. © 2019 The Authors

Background: Double charge exchange (DCE) nuclear reactions have recently attracted much interest as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-β decay. In this framework, a good description of the reaction mechanism and a complete knowledge of the initial and final-state interactions are mandatory. Presently, not enough is known about the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for future DCE studies. Among these, the Ne20+Ge76 DCE reaction is particularly relevant due to its connection with Ge76 double-β decay. Purpose: We intend to characterize the initial-state interaction for the Ne20+Ge76 reactions at 306 MeV bombarding energy and determine the optical potential and the role of the couplings between elastic channel and inelastic transitions to the first low-lying excited states. Methods: We determine the experimental elastic and inelastic scattering cross-section angular distributions, compare the theoretical predictions by adopting different models of optical potentials with the experimental data, and evaluate the coupling effect through the comparison of the distorted-wave Born approximation calculations with the coupled channels ones. Results: Optical models fail to describe the elastic angular distribution above the grazing angle (≈9.4). A correction in the geometry to effectively account for deformation of the involved nuclear systems improves the agreement up to about 14. Coupled channels effects are crucial to obtain good agreement at large angles in the elastic scattering cross section. Conclusions: The analysis of elastic and inelastic scattering data turned out to be a powerful tool to explore the initial and final-state interactions in heavy-ion nuclear reactions at high transferred momenta. © 2019 American Physical Society.

International audience; 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.

Neutrinoless double beta decay (0 nu beta beta) is considered the best potential resource to access the absolute neutrino mass scale. Moreover, if observed, it will signal that neutrinos are their own anti-particles (Majorana particles). Presently, this physics case is one of the most important research “beyond Standard Model” and might guide the way towards a Grand Unified Theory of fundamental interactions. Since the 0 nu beta beta decay process involves nuclei, its analysis necessarily implies nuclear structure issues. In the NURE project, supported by a Starting Grant of the European Research Council (ERC), nuclear reactions of double charge-exchange (DCE) are used as a tool to extract information on the 0 nu beta beta Nuclear Matrix Elements. In DCE reactions and beta beta decay indeed the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute cross-sections can give crucial information on beta beta matrix elements. In a wider view, the NUMEN international collaboration plans a major upgrade of the INFN-LNS facilities in the next years in order to increase the experimental production of nuclei of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest as candidates for 0 nu beta beta.

The article describes the main achievements of the NUMEN project together with an updated and detailed overview of the related R&D activities and theoretical developments. NUMEN proposes an innovative technique to access the nuclear matrix elements entering the expression of the lifetime of the double beta decay by cross section measurements of heavy-ion induced Double Charge Exchange (DCE) reactions. Despite the fact that the two processes, namely neutrinoless double beta decay and DCE reactions, are triggered by the weak and strong interaction respectively, important analogies are suggested. The basic point is the coincidence of the initial and final state many-body wave functions in the two types of processes and the formal similarity of the transition operators. First experimental results obtained at the INFN-LNS laboratory for the 40Ca(18O,18Ne)40Ar reaction at 270MeV give an encouraging indication on the capability of the proposed technique to access relevant quantitative information. The main experimental tools for this project are the K800 Superconducting Cyclotron and MAGNEX spectrometer. The former is used for the acceleration of the required high resolution and low emittance heavy-ion beams and the latter is the large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the experimental resolution and sensitivity required for the accurate measurement of the DCE cross sections at forward angles. However, the tiny values of such cross sections and the resolution requirements demand beam intensities much larger than those manageable with the present facility. The on-going upgrade of the INFN-LNS facilities in this perspective is part of the NUMEN project and will be discussed in the article. © 2018, SIF, Springer-Verlag GmbH Germany, part of Springer Nature.

The NUMEN project proposes to measure the absolute cross sections of heavy-ion induced Double Charge Exchange (DCE) reactions with the final goal to get information on the nuclear matrix elements involved in the neutrinoless double beta (0v beta beta) decay. The knowledge of the nuclear matrix elements is crucial to infer the neutrino average masses from the possible measurement of the half-life of 0v beta beta decay and also to compare experiments on different isotopes. DCE reactions and 0v beta beta decay present some similarities, the initial and final-state wave functions are the same and the transition operators are similar. Many challenges have to be faced for the experimental measurements of DCE reactions induced by heavy ions, since they are characterized by very low cross sections.

The goal of NUMEN project is to access experimentally driven information on Nuclear Matrix Elements (NME) involved in the neutrinoless double beta decay (0v beta beta), 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 0v beta beta decay and to compare experiments on different isotopes. In particular, the (O-18, Ne-18) and (Ne-20, O-20) reactions are performed as tools for beta(+)beta(+) and beta(-)beta(-) 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.

The NUMEN project proposes to study heavy-ion induced Double Charge Exchange (DCE) reactions with the final goal to get information on the nuclear matrix elements for neutrinoless double beta (0v beta beta) decay. The knowledge of the nuclear matrix elements is crucial to infer the neutrino average masses from the possible measurement of the half-life of 0v beta beta decay. DCE reactions and 0v beta beta decay present some similarities, the initial and final-state wave functions are the same and the transition operators are similar. The experimental measurements of DCE reactions induced by heavy ions present a number of challenging aspects, since they are characterized by very low cross sections.

The Muon Portal Project has built a prototype of a real size detector ( 6 m × 3 m × 7 m) for the inspection of containers by muon tomography . This technique may provide 2D and 3D images of the interior of a container, to identify the presence of high- Z materials. In the present Project, 4800 extruded scintillator strips were arranged such as to cover four X–Y detection planes ( 6 m × 3 m), two placed above and two below the container to be inspected. Silicon photomultipliers were used as photosensors , to collect the light transported by Wave Length Shifter (WLS) fibres embedded in the scintillator strips. First tomographic images are here presented.