Double Charge Exchange Reactions Research Articles

Correlation between neutrinoless double-β decay and double Gamow-Teller transitions

The neutrinoless double-β (0νββ) decay and the double Gamow-Teller (DGT) transition are investigated with the state-of-the-art Relativistic Configuration-interaction Density functional theory. A strong linear correlation between the nuclear matrix elements (NMEs) of the 0νββ decay and the DGT transition is demonstrated. This linear correlation is found to originate from the similarity of the leading-order term of the 0νββ-decay operator and the DGT-transition one, as revealed by expanding the 0νββ-decay operator in terms of the spherical harmonics. The present results provide a strong support to constrain the 0νββ-decay NMEs through the double charge-exchange reactions.

Theory of Majorana-Type Heavy Ion Double Charge Exchange Reactions by Pion–Nucleon Isotensor Interactions

The theory of heavy ion double charge exchange (DCE) reactions proceeding by effective rank-2 isotensor interactions is presented. Virtual pion–nucleon charge exchange interactions are investigated as the source for induced isotensor interactions, giving rise to the Majorana DCE (MDCE) reaction mechanism. MDCE is of a generic character, proceeding through pairs of complementary (π±,π∓) reactions in the projectile and target nucleus. The dynamics of the elementary processes is discussed, where the excitation of pion–nucleon resonances are of central importance. Investigations of initial and final state ion–ion interactions show that these effects are acting as vertex renormalizations. In closure approximation, well justified by the finite pion mass, the second-order transition matrix elements reduce to pion potentials and effective two-body isotensor DCE interactions, giving rise also to two-body correlations in either of the participating nuclei. Connections to neutrinoless Majorana double beta decay (MDBD) are elucidated at various levels of the dynamics, from the underlying fundamental electro-weak and QCD scales to the physical scales of nuclear MDBD and MDCE physics. It is pointed out that heavy ion MDCE reactions may also proceed by competing electro-weak charge exchange processes, leading to lepton MDCE by electrons, positrons, and neutrinos.

Formal theory of heavy ion double charge exchange reactions

The theory of heavy ion double charge exchange (DCE) reactions A(Z, N) → A(Z ± 2, N ∓ 2) is recapitulated emphasizing the role of Double Single Charge Exchange (DSCE) and pion-nucleon Majorana DCE (MDCE) reactions. DSCE reactions are of second–order distorted wave character, mediated by isovector nucleon-nucleon (NN) interactions. The DSCE response functions resemble the nuclear matrix elements (NME) of 2ν2β decay. The MDCE process proceeds by a dynamically generated effective rank-2 isotensor interaction, defined by off–shell pion–nucleon DCE scattering. In closure approximation pion potentials and two–nucleon correlations are obtained, similar to the neutrino potentials and the intranuclear exchange of Majorana neutrinos in 0ν2β Majorana double beta decay (MDBD).

Heavy-ion induced double charge exchange reaction in a multi-channel approach: The research program of the NUMEN project

We give an updated view of the status and prospects of heavy-ion double charge exchange (HI-DCE) reaction studies performed at the Laboratori Nazionali del Sud of the Istituto Nazionale di Fisica Nucleare (INFN-LNS) in the context of the NUMEN project. The important role of HI-DCE for nuclear reaction, nuclear structure and double beta-decay investigations is outlined. A powerful way to scrutinize the nuclear response to HI-DCE is to consistently link it to the information extracted from the competing direct reactions pointing to a multi-channel description of the whole network of quasi-elastic processes. Indeed, these complementary studies are mandatory in order to minimize the systematic errors in the data analyses and build a many-facets and parameter-free representation of the systems under study.

New Interacting Boson Fermion-Fermion Model results

We present a new application of the Interacting Boson Model (IBM) and its extensions for describing double charge exchange reactions. The study of double charge exchange reactions induced by heavy ions involving candidate nuclei for neutrinoless double beta decay is a complex task carried out by the NUMEN collaboration. This investigation faces the intricacies of complex oddodd intermediate nuclei in sequential double charge exchange processes. We will offer a comprehensive description of heavy odd-odd nuclei using the Interacting Boson Fermion-Fermion Model (IBFFM). Additionally, we will outline the methodology for describing transfer operators within this framework. Finally, we will explore the potential applications of our results for describing double charge exchange reactions.

Study of single-nucleon transfer reactions in the 18O+48Ti collision at 275 MeV

The study of single-nucleon transfer reactions for the 18O+48Ti system was pursued at the energy of 275 MeV as part of a more systematic study which is undertaken within the NUMEN and NURE experimental campaigns. The aim is to measure the complete set of available reaction network which are characterized by the same initial and final-state wavefunctions as the more suppressed double charge exchange reactions. Understanding the degree of competition between successive nucleon transfer and double charge exchange reactions is crucial for the description of the meson-exchange mechanism. In this respect, angular distribution measurements for one- and twonucleon transfer reactions for the 18O+48Ti system were carried out at theMAGNEX facility of INFN-LNS in Catania. An overview of the data analysis for the 48Ti(18O,19F)47Sc and 48Ti(18O,17O)49Ti reactions will be presented.

Experimental and theoretical multichannel study of direct nuclear reactions: A tool to provide data driven information on neutrino-less double-beta decay

The search for neutrino-less double beta decay has attracted much interest in the last years due to the extraordinary consequences that could derive from its observation. In the view to provide experimental information on the nuclear matrix elements involved in the expression of neutrino-less double beta decay half-life, the NUMEN project is measuring cross-sections of double charge exchange and other quasi-elastic nuclear reactions using the MAGNEX magnetic spectrometer. In particular, the newly proposed multichannel approach, applied both to the experimental and theoretical analysis, will be discussed.

Nuclear Structure Aspects of DCX Reactions and β β Decay Transitions

The theory of Double Charge Exchange (DCX) reactions between nuclei requires both the description of the reaction mechanism, which consists of the exchange of nucleons between the target and the projectile, as well as the structure of the matrix elements of the operators which mediate the transitions. From the point of view of the nuclear structure theory it requires the use of microscopic models for light and heavy mass nuclei. The reaction sector requires the use of momentum-dependent operators. It has been argued that these matrix elements could be associated to decay channels like the neutrinoless nuclear double beta decay (0νββ)(DBD). The motivation related to this claim is the need to determine, as accurately as possible, the values of the matrix elements of operators responsible for 0νββ. We shall focus the attention on the possible relationship between DBD and DCX nuclear matrix elements, by studying the dependence of the participant operators upon the momentum.

Modeling Double Charge Exchange processes occurring in Heavy Ion Reactions

Heavy ion induced double charge exchange reactions are treated as an incoherent sequence of two reactions driven by the exchange of charged mesons (double single charge exchange, DSCE). The process is described within a fully quantum mechanical distorted wave 2-step theory (2nd order DWBA). The DSCE reaction amplitudes are shown to be separable into superpositions of distortion factors, accounting for initial and final state ion-ion elastic interactions, and nuclear matrix elements (NMEs). Explicit expressions of projectile and target NMEs are derived within the QRPA theory. Reduction schemes for the DSCE transition form factors are described, analizing their momentum structure within the closure approximation. Formal analogies between the NMEs involved in DSCE reactions and in double beta decays are also pointed out. Results, obtained within this theoretical framework, are illustrated for the reaction 40Ca (18O, 18Ne)40Ar at 15.3 AMeV and compared to the data measured at INFN-LNS by the NUMEN Collaboration. Furthermore, preliminary results for reactions involving heavier systems, such as 76Se (18O, 18Ne)76Ge, are shown.

Recent results on the analysis of the 18O+48Ti collision at 275 MeV: Single charge exchange reaction

The present work is inherent to the NUMEN project that aims at providing data-driven information for the nuclear matrix elements of the neutrinoless double beta decay through the study of heavy-ion induced double charge exchange reactions. This is a formidable task since during a nuclear collision, the same final states may be populated through various reaction mechanisms. In this respect, understanding the degree of competition between successive nucleon transfer and charge exchange reactions is crucial for the proper description of the meson-exchange mechanism. To this purpose, the reaction dynamics in the 18O+48Ti collision were sought by measuring a plethora of reaction channels under the same experimental conditions. The 48Ti was chosen as target since it is the daughter nucleus of 48Ca in double beta decay. The relevant experiment was performed at the MAGNEX facility of INFN-LNS in Catania. In this contribution, the status of the analysis for the 48Ti(18O,18F)48Sc single charge exchange reaction will be presented.

A multi–channel study of the 20Ne + 130Te system within the NUMEN project

The NUMEN project aims to measure specific reaction cross sections to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double beta decay (0νββ). In particular, it was proposed to use heavy – ion induced double charge exchange reactions as tools towards the determination of information on the nuclear matrix elements of 0νββ, strongly motivated by a number of similarities between the two processes. To this extent, the 20Ne + 130Te system was experimentally investigated in a multi-channel approach by measuring the complete net of reactions channels, namely double charge exchange, single charge exchange, elastic and inelastic scattering, one – and two – nucleon transfer reactions, characterized by the same initial projectile and target nuclei. The goal of the study is to fully characterize the properties of the nuclear wavefunctions entering in the 0νββ decay nuclear matrix elements. The experimental setup, the data reduction and some of the obtained results for the 20Ne + 130Te system will be presented and discussed.

Response of G-NUMEN LaBr3(Ce) Detectors to High Counting Rates

The G-NUMEN array is the future gamma spectrometer of the NUMEN experiment (nuclear matrix element for neutrinoless double beta decay), to be installed around the object point of the MAGNEX magnetic spectrometer at the INFN-LNS laboratory. This project aims to explore double-charge exchange (DCE) reactions in order to obtain crucial information about neutrinoless double beta decay (0νββ). The primary objective of the G-NUMEN array is to detect the gamma rays emitted from the de-excitation of the excited states that are populated via DCE reactions with a good energy resolution and detection efficiency, amidst a background composed of the transitions from competing reaction channels with far higher cross sections. To achieve this, G-NUMEN signals will be processed in coincidence with those generated by the detection of reaction ejectiles by the MAGNEX focal plane detector (FPD). Under the expected experimental conditions, G-NUMEN detectors will operate at high counting rates, of the order of hundreds of kHz per detector, while maintaining excellent energy and timing resolutions. The complete array will consist of over 100 LaBr3(Ce) scintillators. Initial tests were conducted on the first detectors of the array, allowing for the determination of their performance at high rates.

Recent results on the analysis of the 48Ti(18O, 20Ne)46Ca reaction at 275 MeV

The 18O+48Ti reaction was studied at the energy of 275 MeV for the first time under the NUMEN and NURE experimental campaigns with the aim of investigating the complete reaction network potentially involved in the 48Ti→48Ca double charge exchange transition. Understanding the degree of competition between successive nucleon transfer and double charge exchange reactions is crucial for the description of the meson exchange mechanism. Into this context, angular distribution measurements for one- and two-nucleon transfer reactions for the system 18O+48Ti were performed at the MAGNEX facility of INFN-LNS in Catania. An overview of the status of the analysis for the two-proton transfer reaction will be given.

Double charge-exchange reactions for the nuclear matrix elements of neutrinoless double beta decay

Double charge exchange (DCE) reactions induced by heavy ions are crucial tools to access information relevant for neutrinoless double beta decay nuclear matrix elements. In this context the NUMEN project aims to investigate, for each system of interest, the DCE reaction channel together with the whole set of reactions promoted by the same projectile/target interaction in the same experimental conditions and within the same theoretical framework.

New high intensity Heavy - Ion beams @ INFN-LNS: NUMEN project status and perspective

The upgrade project POTLNS to produce high-intensity beams has already started at INFN- Laboratori Nazionali del Sud in Catania (Italy). The POTLNS project was triggered by the NUMEN physics case that aims to provide experimental information on the Nuclear Matrix Elements (NMEs) that enter in the expression of the neutrino-less double beta (0νββ) decay half-life. The tools proposed by NUMEN project are the cross-section measurements of nuclear Double Charge Exchange (DCE) reactions. The search for 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 could provide a crucial contribution in this search.

Heavy-ion induced quasi-elastic reactions in view of the NUMEN project

Double charge exchange (DCE) reactions induced by heavy ions and other direct reactions characterized by same projectile and target are crucial tools to access information relevant for neutrinoless double beta decay nuclear matrix elements. In this context the NUMEN project aims to investigate, for each system of interest, not only the DCE channel but also the whole set of reactions promoted by the same projectile/target interaction in the same experimental conditions and within the same theoretical framework. An example of the application of such a multi-channel approach is presented here.

Study of the one-neutron transfer reaction in 18O + 76Se collision at 275 MeV in the context of the NUMEN project

Heavy-ion one-nucleon transfer reactions are promising tools to investigate single-particle configurations in nuclear states, with and without the excitation of the core degrees of freedom. An accurate determination of the spectroscopic amplitudes of these configurations is essential for the study of other direct reactions as well as beta-decays. In this context, the 76Se(18O,17O)77Se one-neutron transfer reaction gives a quantitative access to the relevant single particle orbitals and core polarization transitions built on 76Se. This is particularly relevant, since it provides data-driven information to constrain nuclear structure models for the 76Se nucleus.The excitation energy spectrum and the differential cross section angular distributions of this nucleon transfer reaction was measured at 275 MeV incident energy for the first time using the MAGNEX large acceptance magnetic spectrometer. The data are compared with calculations based on distorted wave Born approximation and coupled channel Born approximation adopting spectroscopic amplitudes for the projectile and target overlaps derived by large-scale shell model calculations and interacting boson-fermion model.These reactions are studied in the frame of the NUMEN project. The NUMEN (NUclear Matrix Elements for Neutrinoless double beta decay) project was conceived at the Istituto Nazionale di Fisica Nucleare–Laboratori Nazionali del Sud (INFN-LNS) in Catania, Italy, aiming at accessing information about the nuclear matrix elements (NME) of neutrinoless double beta decay (0νββ) through the study of the heavy-ion induced double charge exchange (DCE) reactions on various 0νββ decay candidate targets. Among these, the 76Se nucleus is under investigation since it is the daughter nucleus of 76Ge in the 0νββ decay process.

Integration of the scattering chamber of the NUMEN experiment

The NUMEN experiment points to measure Double Charge Exchange reaction (DCE) cross sections with heavy-ion beams interacting with specific isotopes of interest for Neutrinoless Double Beta Decay process (0νββ). To achieve this, NUMEN requires a complete upgrade to MAGNEX spectrometer in INFN-LNS and a high intensity ion beam. This work focuses on the design of a new scattering chamber where the ion beam will interact with the target precisely positioned by an automatic system. The target will be cooled by a custom system based on HOPG and a cryo-cooler. The fist integration of the chamber with all its components has been done at INFN section of Turin to check compliance with the requirements and to study the procedures for the target replacement. Some results of this tests will be presented.

Transfer reactions between odd-odd and even-even nuclei by using the interacting boson fermion fermion model and 0νββ decay in closure approximation

Spectroscopic amplitudes (SAs) in the interacting boson fermion fermion model (IBFFM) are necessary for the computation of $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay but also for cross sections of heavy-ion reactions, in particular, double charge exchange reactions for the NUMEN Collaboration, if one does not want to use the closure limit. We present for the first time (i) the formalism and operators to compute in a general case the spectroscopic amplitudes in the IBFFM scheme from even-even to odd-odd nuclei, in a way suited to be used in reaction code, i.e., extracting the contribution of each orbital; (2) the odd-odd nuclei as described by the old IBFFM are obtained for the first time with the new implementation of machine learning (ML) techniques for fitting the parameters, getting a more realistic description. The one-body transition densities for $^{116}\mathrm{Cd}\ensuremath{\rightarrow}^{116}\mathrm{In}$ and $^{116}\mathrm{In}\ensuremath{\rightarrow}^{116}\mathrm{Sn}$ are part of the experimental program of the NUMEN experiment, which aims to find constraints on $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay matrix elements. As a first application of the spectroscopic amplitudes we present the calculation of the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ nuclear matrix elements in the IBFFM formalism in closure approximation.

Single- and Double-Charge Exchange Reactions and Nuclear Matrix Element for Double-Beta Decay

Neutrino properties such as the Majorana nature and the masses, which go beyond the standard model, are derived from the experimental double-beta decay (DBD) rate by using the DBD nuclear matrix element (NME). Theoretical evaluations for the NME, however, are very difficult. Single-charge exchange reactions (SCERs) and double-charge exchange reactions (DCERs) are used to study nuclear isospin (τ) and spin (σ) correlations involved in the DBD NME and to theoretically calculate the DBD NME. Single and double τσ NMEs for quasi-particle states are studied by SCERs and DCER. They are found to be reduced with respect to the quasi-particle model NMEs due to the τσ correlations. The impact of the SCER- and DCER-NMEs on the DBD NME is discussed.