Search

Two-nucleon transfer reactions are essential tools to investigate specific features of the nuclear structure, such as the correlation among valence particles in the transfer process. Besides, transfer reactions may be an important channel to take into account in charge-exchange processes since they can represent a competing contribution to the final cross section. The two-proton pickup transfer reaction $^{40}\mathrm{Ca}(^{18}\mathrm{O},^{20}\mathrm{Ne})\phantom{\rule{0.16em}{0ex}}^{38}\mathrm{Ar}$ has been measured at 270 MeV, and the angular distributions for transitions to different excited states extracted. This paper shows the analysis of the data performed by finite-range coupled reaction channel and coupled-channel Born approximation methods. Extensive shell-model calculations are performed to derive the one- and two-proton spectroscopic amplitudes for the projectile and target overlaps. The role of the simultaneous and sequential two-proton transfer mechanisms to populate the measured final states or groups of states, mainly characterized by a high collectivity, is also discussed.

Gamma-ray angular distributions in oriented $$^{92}$$ Mo produced via the $$^{6}$$ Li+ $$^{89}$$ Y reaction were studied in this work. The characteristic $$\gamma $$ rays in $$^{92}$$ Mo were measured by means of the GALILEO array, which is composed of 25 Compton-suppressed HPGe detectors arranged in a nearly 2 $$\pi $$ geometry. A detailed analysis of the spin-alignment attenuation factors ( $$\alpha _2$$ ) for different excited states in $$^{92}$$ Mo was performed, by analyzing the measured angular distribution coefficients of several pure-E2 transitions. The relationship between $$\alpha _2$$ and the spin was established in $$^{92}$$ Mo and the 244-keV transition between the 5 $$^-_1$$ and 4 $$^+_1$$ states resulted to have a E1 + M2 character with a mixing ratio ( $$\delta $$ ) of $$-0.05^{+0.05}_{-0.06}$$ , consistent with shell model calculations.

The mechanism of reactions with weakly-bound proton-rich nuclei at energies near the Coulomb barrier is a long-standing open question owing to the paucity of experimental data. In this study, a complete kinematics measurement was performed for the proton drip-line nucleus 17F interacting with 58Ni at four energies near the Coulomb barrier. Thanks to the powerful performance of the detector array, exhaustive information on the reaction channels, such as the differential cross sections for quasielastic scattering, exclusive and inclusive breakup, as well as for fusion-evaporation protons and alphas, was derived for the first time. The angular distributions of quasielastic scattering and exclusive breakup can be described reasonably well by the continuum-discretized coupled-channels calculations. The inclusive breakup was investigated using the three-body model proposed by Ichimura, Austern, and Vincent, and results indicate the non-elastic breakup is the dominant component. The total fusion cross sections were determined by the fusion-evaporation protons and alphas. Based on the measured exclusive breakup data, the analysis of the classical dynamical simulation code PLATYPUS demonstrates that the incomplete fusion plays a minor role. Moreover, compared with 16O+58Ni, both the reaction and total fusion cross sections of 17F+58Ni exhibit an enhancement in the sub-barrier energy region, which mainly arises from couplings to the continuum states. This work indicates that the information of full reaction channels is crucially important to comprehensively understand the reaction mechanisms of weakly bound nuclear systems.

Background: Heavy-ion induced two-nucleon transfer reactions are powerful tools to reveal peculiar aspects of the atomic nucleus, such as pairing correlations, single-particle and collective degrees of freedom, and more. Also, these processes are in competition with the direct meson exchange in the double charge exchange reactions, which have recently attracted great interest due to their possible connection to neutrinoless double-beta decay. In this framework, the exploration of two-nucleon transfer reactions in the 20Ne+116Cd collision at energies above the Coulomb barrier is particularly relevant since the 116Cd nucleus is a candidate for the double-beta decay. Methods: We measured the excitation energy spectra and absolute cross sections for the two reactions using the MAGNEX large acceptance magnetic spectrometer to detect the ejectiles. We performed direct coupled reaction channels and sequential distorted wave Born approximation calculations using the double folding S\~ao Paulo potential to model the initial and final state interactions. The spectroscopic amplitudes for two- and singleparticle transitions were derived by different nuclear structure approaches: microscopic large-scale shell model, interacting boson model-2 and quasiparticle random phase approximation. Results: The calculations are able to reproduce the experimental cross sections for both two-neutron and twoproton transfer reactions. The role of couplings with the inelastic channels are found to be important in the two-proton transfer case. A competition between the direct and the sequential process is found in the reaction mechanism. For the two-proton transfer case, the inclusion of the 1g7/2 and 2d5/2 orbitals in the model space is crucial.

In a recent paper (Chian et al., 2016) it was shown that magnetic reconnection at the interface region between two magnetic flux ropes is responsible for the genesis of interplanetary intermittent turbulence. The normalized third-order moment (skewness) and the normalized fourth-order moment (kurtosis) display a quadratic relation with a parabolic shape that is commonly observed in observational data from turbulence in fluids and plasmas, and is linked to non-Gaussian fluctuations due to coherent structures. In this paper we perform a detailed study of the relation between the skewness and the kurtosis of the modulus of the magnetic field |B| during a triple interplanetary magnetic flux rope event. In addition, we investigate the skewness–kurtosis relation of two-point differences of |B| for the same event. The parabolic relation displays scale dependence and is found to be enhanced during magnetic reconnection, rendering support for the generation of non-Gaussian coherent structures via rope–rope magnetic reconnection. Our results also indicate that a direct coupling between the scales of magnetic flux ropes and the scales within the inertial subrange occurs in the solar wind. Keywords. Space plasma physics (turbulence)

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.

In this work, we revisit the experimental data for elastic, inelastic and $\alpha$-transfer in the 12C + 16O system at 80 and 84 MeV using the coupled reaction channel method to analyze the angular distributions. The spectroscopic amplitudes relevant for the $\alpha$-transfer channel have been calculated from the semi-microscopic algebraic cluster model. The imaginary term of the optical potential was fitted to the experimental elastic scattering data at forward angles. Our calculations describe reasonable well the absolute cross sections for the inelastic scattering and $\alpha$-transfer. We discuss the effect of couplings on the transfer channel.

An updated overview of recent results on Heavy-Ion induced reactions of interest for neutrinoless double beta decay is reported in the framework of the NUMEN project. The NUMEN idea is to study heavy-ion induced Double Charge Exchange (DCE) reactions with the aim to get information on the nuclear matrix elements for neutrinoless double beta (0νββ) decay. Moreover, to infer the neutrino average masses from the possible measurement of the half- life of 0νββ decay, the knowledge of the nuclear matrix elements is a crucial aspect. Uma visão geral atualizada dos resultados recentes sobre reações induzidas por íons pesados ​​de interesse para o decaimento beta duplo sem neutrinos é relatada na estrutura do projeto NUMEN. A ideia do NUMEN é estudar reações de Double Charge Exchange (DCE) induzidas por íons pesados ​​com o objetivo de obter informações sobre os elementos da matriz nuclear para o decaimento beta duplo sem neutrinos (0νββ). Além disso, para inferir as massas médias dos neutrinos a partir da possível medição da meia-vida do decaimento 0νββ, o conhecimento dos elementos da matriz nuclear é um aspecto crucial. 1308 012002

International audience; NUMEN 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. First evidence about the possibility to get quantitative information about NME from experiments is found for the (^18O,^18Ne) and (^20Ne,^20O) reactions. Moreover, to infer the neutrino average masses from the possible measurement of the half-life of 0νββ decay, the knowledge of the NME is a crucial aspect. The key tools for this project are the high resolution Superconducting Cyclotron beams and the MAGNEX magnetic spectrometer at INFN Laboratori Nazionali del Sud in Catania (Italy). The measured cross sections are extremely 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.

Background: Recently, a systematic exploration of two-neutron transfer induced by the $(^{18}\mathrm{O},\phantom{\rule{0.16em}{0ex}}^{16}\mathrm{O})$ reaction on different targets has been performed. The high-resolution data have been collected at the MAGNEX magnetic spectrometer of the INFN-LNS Laboratory in Catania and analyzed with the coupled reaction channel (CRC) approach. The simultaneous and sequential transfers of the two neutrons have been considered under the same theoretical framework without the need for adjustable factors in the calculations.Purpose: A detailed analysis of the one-neutron transfer cross sections is important to study the sequential two-neutron transfer. Here, we examine the $(^{18}\mathrm{O},\phantom{\rule{0.16em}{0ex}}^{17}\mathrm{O})$ reaction on $^{16}\mathrm{O},\phantom{\rule{0.28em}{0ex}}^{28}\mathrm{Si}$, and $^{64}\mathrm{Ni}$ targets. These even-even nuclei allow for investigation of one-neutron transfer in distinct nuclear shell spaces.Method: The MAGNEX spectrometer was used to measure mass spectra of ejectiles and extract differential cross sections of one-neutron transfer to low-lying states. We adopted the same CRC formalism used in the sequential two-neutron transfer, including relevant channels and using spectroscopic amplitudes obtained from shell-model calculations. We also compare with the one-step distorted-wave Born approximation (DWBA).Results: For the $^{18}\mathrm{O}+^{16}\mathrm{O}$ and the $^{18}\mathrm{O}+^{28}\mathrm{O}$ systems, we used two interactions in the shell model. The experimental angular distributions are reasonably well reproduced by the CRC calculations. In the $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ system, we considered only one interaction, and the theoretical curve describes the shape and order of magnitude observed in the experimental data.Conclusions: Comparisons between experimental DWBA and CRC angle-integrated cross sections suggest that excitations before or after the transfer of a neutron are relevant in the $^{18}\mathrm{O}+^{16}\mathrm{O}$ and $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ systems.

International audience; 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$^{40}$Ca($^{18}$O,$^{18}$Ne)$^{40}$Ar 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.

In this paper, we analyze the one-neutron pick-up from the 55Mn target when it is bombarded by 17MeV deuteron, by performing coupled reaction channel (CRC) calculations. Spectroscopic amplitudes for CRC calculations, and structural information such as reduced B(E2) transition probabilities, quadrupole, and magnetic momenta, are obtained from shell-model calculations using the fp-kb3 interaction. The calculated structure quantities are in good agreement with the available experimental data for both target and ejectile. Analyses of angular distributions show the relevance of microscopic information for the description of the higher excited states of 54Mn .

In this work we study the simultaneous and sequential two-neutron transfer mechanisms to the $^{28}\mathrm{Si}$ nucleus induced by $(t,p)$ and $(^{18}\mathrm{O},^{16}\mathrm{O})$ reactions. New experimental cross sections for the $^{28}\mathrm{Si}(^{18}\mathrm{O},^{16}\mathrm{O})^{30}\mathrm{Si}$ reaction at 84 MeV are also presented. Direct reaction calculations are carried out within the exact finite range coupled reaction channel, for the simultaneous transfer of the two-neutron cluster, and the second-order distorted wave Born approximation, for the sequential transfer. Two different models are considered to describe the two-neutron cluster. The spectroscopic information was obtained from a shell-model calculation with a psdmod interaction for the target overlaps where the $1{p}_{3/2}, 1{p}_{1/2}, 1{d}_{3/2}, 1{d}_{5/2}$, and $2{s}_{1/2}$ orbitals are included as valence subspace. We show that simultaneous and sequential two-neutron transfers are competing mechanisms for the population of the ground state in $^{30}\mathrm{Si}$. A systematic analysis of the two-neutron transfer induced by the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction indicates that the static deformation of target nuclei impacts the two-neutron transfer mechanism.

The measurement of one-neutron stripping cross sections for the $^{89}\mathrm{Y}(^{6}\mathrm{Li},^{5}\mathrm{Li})^{90}\mathrm{Y}^{*}$ reaction at 22 MeV and 34 MeV is reported, using both in-beam and off-beam $\ensuremath{\gamma}$-ray spectroscopy methods. Characteristic $\ensuremath{\gamma}$ lines of $^{90}\mathrm{Y}$ are clearly identified by both the $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ and proton-$\ensuremath{\gamma}$ coincidence methods. The obtained cross section of one-neutron stripping at 34 MeV is found to be much smaller than that at 22 MeV. The one-neutron stripping cross sections measured for this system have the same order of magnitude as the one measured for the same reaction for the $^{6}\mathrm{Li}+^{96}\mathrm{Zr}$ system at energies around the Coulomb barrier. Parameter-free coupled reaction channel calculations agree quite well with the experimental data. Theoretical study of the effect of the one-neutron transfer on the elastic total fusion cross section is performed.

We present a brief review of the reaction mechanisms involved in collisions of weakly bound projectiles with tightly bound targets, at near-barrier energies. We discuss systematic behaviors of the data, with emphasis in fusion, breakup, nucleon transfer and elastic scattering. The dependence of the breakup cross section on the charge and mass of the target is discussed, and the influence of the breakup channel on complete fusion is investigated. For this purpose, we compare reduced fusion cross sections with a benchmark universal curve. The behaviors observed in the comparisons are explained in terms of polarization potentials and of nucleon transfer followed by breakup. The influence of the breakup process on elastic scattering is also discussed. Some apparent contradictions between results of different authors are explained and some perspectives of the field are presented.

Recently, various two-neutron transfer studies using the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction were performed with a large success. This was achieved because of a combined use of the microscopic quantum description of the reaction mechanism and of the nuclear structure. In the present work we use this methodology to study the two-neutron transfer reaction of the $^{18}\mathrm{O}+^{64}\mathrm{Ni}$ system at 84 MeV incident energy, to the ground and first ${2}^{+}$ excited state of the residual $^{66}\mathrm{Ni}$ nucleus. All the experimental data were measured by the large acceptance MAGNEX spectrometer at the Instituto Nazionale di Fisica Nucleare --Laboratori Nazionali del Sud (Italy). We have performed exact finite range cross section calculations using the coupled channel Born approximation (CCBA) and coupled reaction channel (CRC) method for the sequential and direct two-neutron transfers, respectively. Moreover, this is the first time that the formalism of the microscopic interaction boson model (IBM-2) was applied to a two-neutron transfer reaction. From our results we conclude that for two-neutron transfer to the ground state of $^{66}\mathrm{Ni}$, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of $^{66}\mathrm{Ni}$, the sequential process dominates. A competition between long-range and short-range correlations is discussed, in particular, how the use of two different models (Shell model and IBM's) help to disentangle long- and short-range correlations.

Background: In our recent work [M. J. Ermamatov et al., Phys. Rev. C 94, 024610 (2016)], the two-neutron transfer induced by the $(^{18}\mathrm{O},^{16}\mathrm{O})$ reaction was studied for $^{16}\mathrm{O}$ nucleus. Theoretical analysis of the low-lying states of $^{18}\mathrm{O}$ indicates that the transfer to the ground state proceeds predominantly through simultaneous transfer of the two-neutron system.Purpose: In this work, we extend our previous theoretical analysis towards high-lying states of the $^{18}\mathrm{O}$ nucleus. In order to achieve a comprehensive picture, we revisit the experimental data for the $^{16}\mathrm{O}(t,p)^{18}\mathrm{O}$ reaction at 15 MeV bombarding energy. We also include new experimental cross sections for the high-lying states of the $^{18}\mathrm{O}$ residual nucleus, populated in the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ reaction at 84 MeV.Method: The same spectroscopic parameters of the target nucleus were used as input in the coupled channel calculations for the transfer induced by triton and $^{18}\mathrm{O}$ projectiles. Simultaneous two-neutron transfer is calculated within the coupled reaction channel approach, using the extreme cluster and independent coordinate models. The sequential process is calculated within the distorted-wave Born approximation.Results: Theoretical calculations reproduce the $^{16}\mathrm{O}(t,p)^{18}\mathrm{O}$ data well, leading to natural parity states in the $^{18}\mathrm{O}$ nucleus without the need of adjustable parameters. The same methods are applied to the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ data and a good agreement is observed.Conclusions: Detailed analyses show the importance of a simultaneous mechanism for the two-neutron transfer reactions. In transferring two neutrons, the pairing correlation plays an important role.

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 Heavy Ion (HI) induced Double Charge Exchange (DCE) reaction cross sections. In particular, the (18O,18Ne) and (20Ne,20O) reactions are used as tools for β+β+ and β−β− decays, respectively. 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 ejectiles are detected the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low (a few nb), being the total reaction cross section much larger (a few b), thus a high sensitivity and a large rejection capability are demanded to the experimental set-up. This limits 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, still keeping the high sensitivity of the present set-up, making it 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 are being developed in order to extract the nuclear structure information from the measured cross sections.

This paper presents values of complete fusion cross sections deduced from activation measurements for the reactions $\phantom{\rule{0.16em}{0ex}}^{6}\mathrm{Li}+\phantom{\rule{0.16em}{0ex}}^{120}\mathrm{Sn}$ and $\phantom{\rule{0.16em}{0ex}}^{7}\mathrm{Li}+\phantom{\rule{0.16em}{0ex}}^{119}\mathrm{Sn}$, and for a projectile energy range from 17.5 to 28 MeV in the center-of-mass system. A new deconvolution analysis technique is used to link the basic activation data to the actual fusion excitation function. The complete fusion cross sections above the barrier are suppressed by about $70%$ and $85%$ with respect to the universal fusion function, used as a standard reference, in the $\phantom{\rule{0.16em}{0ex}}^{6}\mathrm{Li}$ and $\phantom{\rule{0.16em}{0ex}}^{7}\mathrm{Li}$ induced reactions, respectively. From a comparison of the excitation functions of the two systems at energies below the barrier, no significant differences can be observed, despite the two systems have different $n$-transfer $Q$ values. This observation is supported by the results of coupled reaction channels (CRC) calculations.

The $^{13}\mathrm{C}(^{18}\mathrm{O},^{16}\mathrm{O})^{15}\mathrm{C}$ reaction is studied at 84 MeV incident energy. Excitation energy spectra and absolute cross-section angular distributions for the strongest transitions are measured with good energy and angular resolutions. Strong selectivity for two-neutron configurations in the states of the residual nucleus is found. The measured cross-section angular distributions are analyzed by exact finite-range coupled reaction channel calculations. The two-particle wave functions are extracted using the extreme cluster and the independent coordinate scheme with shell-model derived coupling strengths. A new approach also is introduced, the microscopic cluster, in which the spectroscopic amplitudes in the center-of-mass reference frame are derived from shell-model calculations using the Moshinsky transformation brackets. This new model is able to describe well the experimental cross section and to highlight cluster configurations in the involved wave functions.

Recently a quantitative description of the two-neutron transfer reaction $^{12}\mathrm{C}(^{18}\mathrm{O},^{16}\mathrm{O})^{14}\mathrm{C}$ was performed and the measured cross sections were successfully reproduced [M. Cavallaro et al., Phys. Rev. C 88, 054601 (2013)]. This task was accomplished by combining nuclear structure calculations of spectroscopic amplitudes and a full quantum description of the reaction mechanism. Verification of such a theoretical approach to other heavy nuclear systems is mandatory in order to use ($^{18}\mathrm{O},^{16}\mathrm{O}$) reactions to assess pair configurations in nuclear states. In this work we apply this methodology to the $^{16}\mathrm{O}(^{18}\mathrm{O},^{16}\mathrm{O})^{18}\mathrm{O}$ reaction at 84 MeV. Experimental angular distributions for the two-neutron transfer to the ground state and ${2}_{1}^{+}$ state of $^{18}\mathrm{O}$ were obtained using the MAGNEX spectrometer at INFN-LNS. The roles of one- and two-step processes are analyzed under the exact finite range coupled reaction channel and the second order distorted wave Born approximation. We conclude that the one-step transfer mechanism is dominant in this system.

Neutrinoless double beta decay (0v\b{eta}\b{eta}) 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 0v\b{eta}\b{eta} 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 0v\b{eta}\b{eta} Nuclear Matrix Elements. In DCE reactions and \b{eta}\b{eta} 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 \b{eta}\b{eta} 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 0v\b{eta}\b{eta}.

In the present paper it is described an analysis procedure suited for experiments where cross-sections strongly varying with energy are measured using beams having large energy dispersion. These cross-sections are typically the sub-barrier fusion excitation function of reactions induced by radioactive beams. The large beam energy dispersion, typical of these experiments, can lead to ambiguities in the association of the effective beam energy to the reaction product yields and consequently to an error in the determination of the excitation function. As a test case, the approach is applied to the experiments 6 Li+120 Sn and 7 Li+119 Sn measured in the energy range 14 MeV ≤ Ec.m. ≤28 MeV. The complete fusion cross sections are deduced from activation measurements using the stacked target technique. The results of these experiments, that employ the two weakly-bound stable Li isotopes, show that the complete fusion cross sections above the barrier are suppressed of about 70% and 85% with respect to the Universal Fusion Function, used as a standard reference, in the 6 Li and 7 Li induced reactions respectively. Moreover, the excitation functions of the two systems at energies below the barrier, do not show significant differences, despite the two systems have different n -transfer Qvalue .

The Giant Pairing Vibration (GPV) is a correlated two-nucleon excitation mode in atomic nuclei predicted long time ago. It is expected to be excited in two-nucleon transfer reactions, similarly to the pairing vibrations feeding the ground states of even-even nuclei near shell-closure. Recent experiments have provided evidence for this mode in $$^{\mathrm {14}}$$ C and $$^{\mathrm {15}}$$ C nuclei populated via $$^{\mathrm {12}}$$ C, $$^{\mathrm {13}}$$ C( $$^{\mathrm {18}}$$ O, $$^{\mathrm {16}}$$ O) $$^{\mathrm {14}}$$ C, $$^{\mathrm {15}}$$ C two-neutron transfer reactions at 84 MeV beam energy. In the present paper, new data show the persistence of the same structures in the energy spectra of $$^{\mathrm {14}}$$ C and $$^{\mathrm {15}}$$ C populated by the same reactions at a higher bombarding energy of 275 MeV. The extracted centroid, width, spin-parity and transition probability fully agree with the previous observation thus giving a robust confirmation that the GPV mode is populated in such transfer reactions.

Neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) is considered the best potential resource to determine the absolute neutrino mass scale. Moreover, if observed, it will signal that the total lepton number is not conserved and neutrinos are their own anti-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 \b{eta}\b{eta} decay process involves nuclei, its analysis necessarily implies nuclear structure issues. The 0{\nu}\b{eta}\b{eta} decay rate can be expressed as a product of independent factors: the phase-space factors, the nuclear matrix elements (NME) and a function of the masses of the neutrino species. Thus the knowledge of the NME can give information on the neutrino mass scale, if the 0{\nu}\b{eta}\b{eta} decay rate is measured. In the NURE project, supported by a Starting Grant of the European Research Council, nuclear reactions of double charge-exchange (DCE) will be used as a tool to extract information on the \b{eta}\b{eta} NME. In DCE reactions and \b{eta}\b{eta} decay, the initial and final nuclear states are the same and the transition operators have similar structure. Thus the measurement of the DCE absolute crosssections can give crucial information on \b{eta}\b{eta} matrix elements., Comment: arXiv admin note: substantial text overlap with arXiv:2001.09657; text overlap with arXiv:2001.09648

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). In this view measurements of Heavy Ion (HI) induced Double Charge Exchange (DCE) reaction cross sections are performed with high-accuracy. In particular, the (18O,18Ne) and (20Ne,20O) reactions are used as tools for β+β+ and β-β- decays, respectively. 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 ejectiles are detected the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low (a few nb), being the total reaction cross section much larger (a few b), thus a high sensitivity and a large rejection capability are demanded to the experimental set-up. This limits 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 under way in order to increase the experimental dataset of more than two orders of magnitude, still preserving the high sensitivity of the present set-up. When accomplished this effort will make the INFN-LNS as the state-of-the-art research infrastructure for the systematic study of all the cases of interest for 0νββ. In this view, frontiers technologies are going to be adopted for the accelerator and the detection systems. In parallel, advanced theoretical models are being developed in order to extract the nuclear structure information from the measured cross sections.