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Background: Single-charge-exchange reactions are appropriate tools to study the nuclear response to one-particle/one-hole isospin probes, gaining additional interest from the connection to beta decay. This analogy has been recently extended to second order, connecting double-charge-exchange reactions and double beta decays. Nowadays, the availability of powerful experimental setups and advanced nuclear theories and models allows one to access precious information on key nuclear structure aspects embedded in the widely sought neutrinoless double beta decay. Purpose: We intend to bring to light the main nuclear structure and reaction features involved in the O18+C12 collision at 275 MeV incident energy. In this paper, the main focus is on the role of the initial- and final-state interactions in the overall reaction dynamics and on the single-particle nuclear structure properties accessed via the study of single-nucleon transfer reactions. Forthcoming articles will be devoted to go into the details of the response to one- and two-particle/hole isospin probes. Methods: Cross-section energy spectra and angular distributions were measured in a unique experimental setup for the C12(O18,O18)C12 elastic and inelastic scattering, the C12(O18,O17)C13 one-neutron stripping, the C12(O18,F19)B11 one-proton pickup, and the C12(O18,F18)B12 single-charge-exchange nuclear reactions. A unique comprehensive and coherent theoretical calculation, able to describe the whole network of direct reactions using state-of-the-art nuclear structure and reaction theories, was performed, and it is presented for the first time in this article. This holistic approach, applied both to the experimental and theoretical analysis, is the main feature and worth of the work here presented. Results: The energy and angular resolutions achieved in each reaction channel allowed us to isolate specific transitions and to map the diffraction patterns in the angular distributions. The cross-section calculations describe well the experimental data, both in terms of the absolute values and diffraction patterns. Although the distorted wave Born approximation (DWBA) calculations prove to be accurate in describing all the studied channels, better results are achieved when the couplings to inelastic transitions in both the incoming and outgoing partitions are introduced, as done in the coupled channels Born approximation (CCBA) calculations. Otherwise, no real improvement is found when the coupling effects among different partitions are explicitly taken into account in the coupled reaction channels (CRC) calculations. Conclusions: The multichannel approach proposed in this paper is a promising method for accurate investigations of direct reactions originating in heavy-ion collisions. This is quite appealing for the precise spectroscopy of heavy nuclei proposed in many areas of nuclear physics. An example is the NUMEN project with its challenging commitment to provide valuable information on neutrinoless double beta decay nuclear matrix elements from single- and double-charge-exchange cross-section measurements.

The present paper analyses the current results and pursuits the main steps required for the design of SF-QED experiments at High-Power Laser System (HPLS) of ELI-NP in Magurele, Romania. After a brief analysis of the first experiment (E-144 SLAC), which confirmed the existence of non-linear QED interactions of the high energy electrons with the photons of a laser beam, we went on to present fundamental QED processes possible to be studied at ELI-NP in a multi-photon regime. The kinematics and characteristic parameters of the laser beam interacting with electrons were presented. In the preparation of an experiment at ELI-NP, the analysis of the kinematics and dynamics of the non-linear QED interaction processes with the physical vacuum are required. Initially, the linear QED processes and the corresponding Feynman diagrams that allow to determine the amplitude of these processes are reviewed. Based on these amplitudes, the cross sections of the processes can be obtained. For multi-photon interactions it is necessary to adapt the technique of Feynman diagrams from linear QED processes to the non-linear ones, by moving to the quantum field description with dressed Dirac-Volkov states, for particles in intense EM field. They then allow evaluation of the amplitude of the physical processes and ultimately the determination of the corresponding cross section. The SF-QED processes of multi-photon interactions with strong laser fields, can be done taking into account the characteristics of the existing facilities at ELI-NP in the context of the experimental production of electron-positron-pairs and of energetic gamma-rays. We show also some upcoming experiments similar to ours, in various stages of preparation., Presented at Bucharest University Meeting 2023 https://ssffb.fizica.unibuc.ro/SSFFB/Section.php?SectID=221

Background: Nucleon transfer reactions are selective tools for nuclear physics investigations. The theoretical and computational limits affecting in the past their data analysis could be nowadays surmounted thanks to the advent of methods with refined approximations and constraints, even when heavy-ion collisions are considered. Purpose: Modern microscopic calculations of heavy-ion-induced transfer reactions combined with precise experimental data offer the chance for accurately testing different reaction models as well as the nuclear structure description of the involved nuclear states. Method: Single proton and neutron transfer reactions were measured with the MAGNEX magnetic spectrometer for the O18+Ca40 system at 15.3A MeV. Excitation energy spectra and angular differential cross section distributions were extracted. The experimental results are compared with theoretical calculations performed in distorted wave and coupled channel Born approximation. The use of a coupled channel equivalent polarization potential to effectively describe the coupling effects affecting the initial state interaction is also considered. Spectroscopic amplitudes derived from a large-scale shell model with appropriate interactions adapted for the involved nuclei are employed. Results: Our theoretical calculations are in good agreement with experimental data, without the need for any scaling factor, validating the adopted reaction and nuclear structure parameters. Moreover, under the present experimental conditions, a weak dependence of the obtained results on the choice of the reaction models was observed. Conclusions: The good agreement between experimental and theoretical results validates the reliability of the parameter sets entering the calculations. They are extracted from or tested in complementary analyses of other reaction channels under the same experimental conditions. Such a multichannel approach represents the best option to pursue a solid, comprehensive, and model-independent description of the single-nucleon transfer reactions. The successful description of the present one-nucleon transfer data is also propaedeutic to the accurate assessment, under the same theoretical description, of higher-order transfer processes, like the sequential nucleon transfer mechanisms which are in competition with the direct charge exchange reactions.

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. © 2021 Cavallaro, Bellone, Calabrese, Agodi, Burrello, Cappuzzello, Carbone, Colonna, Deshmukh, Lenske, Spatafora, Acosta, Amador-Valenzuela, Borello-Lewin, Brischetto, Calvo, Capirossi, Chávez, Ciraldo, Cutuli, Delaunay, Djapo, Eke, Finocchiaro, Firat, Fisichella, Foti, Guazzelli, Hacisalihoglu, Iazzi, Fauci, Linares, Lubian, Medina, Moralles, Oliveira, Pakou, Pandola, Petrascu, Pinna, Russo, Sgouros, Solakci, Soukeras, Souliotis, Torresi, Tudisco, Yildirin and Zagatto.

Background: An accurate description of the initial and final state interactions in the O-18 + Se-76 collision is demanded by the NUMEN project. The study of single and double charge exchange nuclear reactions is the main purpose for NUMEN, since these can be used as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-beta decay. To date, the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for the NUMEN double charge exchange studies are poorly known. The O-18 + Se-76 case, here under study, is particularly relevant due to its connection with the Ge-76 neutrinoless double-beta decay. Purpose: In this work the authors want to characterize the initial-state interaction for the O-1(8) + Se-76 reactions at 275 MeV incident energy determining the optical potential and evaluating the effect of couplings with the inelastic scattering on the elastic channel. Methods: The angular distributions of differential cross section were measured in the angular region between 4 degrees and 22 degrees in the center-of-mass reference frame. The cross sections were compared with theoretical calculations, that adopt different optical potentials. Coupling effects on the elastic channel were determined into the coupled channels formalism. Results: The excitation energy spectrum of the colliding nuclei and the cross section angular distributions were measured with satisfactory energy resolution. The elastic scattering cross section is not well reproduced in the full angular range explored when the optical model approach is adopted. A good agreement is found using coupled channel calculations. The initial state interaction for the O-18 + Se-76 nuclear reactions at 275 MeV is determined. Conclusions: Coupled channels effects are crucial to obtain a good description of the measured elastic and inelastic channels cross sections, even at large transferred momenta where the optical model approach fails in reproducing the experimental data. The role of channel coupling could be relevant also in the analysis of other open reaction channels in the same collision and should be accounted for in double charge exchange analyses as well.

The Te-130(Ne-20, O-20) Xe-130 double charge exchange reaction was measured for the first time at very forward angles with the MAGNEX magnetic spectrometer at INFN-LNS. The study, performed at beam energy of 306 MeV, is part of a systematic exploration promoted by the NUMEN project. The last 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.

Double charge exchange (DCE) reactions could provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-β decay. To achieve this goal, a detailed description of the reaction mechanism is mandatory. This requires the full characterization of the initial and final-state interactions, which are poorly known for many of the projectile-target systems involved in future DCE studies. Among these, we intend to study the20 Ne +130 Te and18 O +116 Sn systems at 15.3 AMeV, which are particularly relevant due to their connection with the130 Te→130 Xe and116 Cd→116 Sn double-β decays. We measure the elastic and inelastic scattering cross-section angular distributions and compare them with theoretical calculations performed in the optical model, one-step distorted wave Born approximation, and coupled-channel approaches using the São Paulo double-folding optical potential. A good description of the experimental data in the whole explored range of transferred momenta is obtained provided that couplings with the 2+1 states of the projectile and target are explicitly included within the coupled-channel approach. These results are relevant also in the analysis of other quasi-elastic reaction channels in these systems, in which the same couplings should be included. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

International audience; Background: Nucleon transfer reactions are selective tools for nuclear physics investigations. The theoretical and computational limits affecting in the past their data analysis could be nowadays surmounted thanks to the advent of methods with refined approximations and constraints, even when heavy-ion collisions are considered.Purpose: Modern microscopic calculations of heavy-ion-induced transfer reactions combined with precise experimental data offer the chance for accurately testing different reaction models as well as the nuclear structure description of the involved nuclear states.Method: Single proton and neutron transfer reactions were measured with the MAGNEX magnetic spectrometer for the O18+Ca40 system at 15.3A MeV. Excitation energy spectra and angular differential cross section distributions were extracted. The experimental results are compared with theoretical calculations performed in distorted wave and coupled channel Born approximation. The use of a coupled channel equivalent polarization potential to effectively describe the coupling effects affecting the initial state interaction is also considered. Spectroscopic amplitudes derived from a large-scale shell model with appropriate interactions adapted for the involved nuclei are employed.Results: Our theoretical calculations are in good agreement with experimental data, without the need for any scaling factor, validating the adopted reaction and nuclear structure parameters. Moreover, under the present experimental conditions, a weak dependence of the obtained results on the choice of the reaction models was observed.Conclusions: The good agreement between experimental and theoretical results validates the reliability of the parameter sets entering the calculations. They are extracted from or tested in complementary analyses of other reaction channels under the same experimental conditions. Such a multichannel approach represents the best option to pursue a solid, comprehensive, and model-independent description of the single-nucleon transfer reactions. The successful description of the present one-nucleon transfer data is also propaedeutic to the accurate assessment, under the same theoretical description, of higher-order transfer processes, like the sequential nucleon transfer mechanisms which are in competition with the direct charge exchange reactions.

Background: Nucleon transfer reactions are selective tools for nuclear physics investigations. The theoretical and computational limits affecting in the past their data analysis could be nowadays surmounted thanks to the advent of methods with refined approximations and constraints, even when heavy-ion collisions are considered. Purpose: Modern microscopic calculations of heavy-ion-induced transfer reactions combined with precise experimental data offer the chance for accurately testing different reaction models as well as the nuclear structure description of the involved nuclear states. Method: Single proton and neutron transfer reactions were measured with the MAGNEX magnetic spectrometer for the O-18 + Ca-40 system at 15.3A MeV. Excitation energy spectra and angular differential cross section distributions were extracted. The experimental results are compared with theoretical calculations performed in distorted wave and coupled channel Born approximation. The use of a coupled channel equivalent polarization potential to effectively describe the coupling effects affecting the initial state interaction is also considered. Spectroscopic amplitudes derived from a large-scale shell model with appropriate interactions adapted for the involved nuclei are employed. Results: Our theoretical calculations are in good agreement with experimental data, without the need for any scaling factor, validating the adopted reaction and nuclear structure parameters. Moreover, under the present experimental conditions, a weak dependence of the obtained results on the choice of the reaction models was observed. Conclusions: The good agreement between experimental and theoretical results validates the reliability of the parameter sets entering the calculations. They are extracted from or tested in complementary analyses of other reaction channels under the same experimental conditions. Such a multichannel approach represents the best option to pursue a solid, comprehensive, and model-independent description of the single-nucleon transfer reactions. The successful description of the present one-nucleon transfer data is also propaedeutic to the accurate assessment, under the same theoretical description, of higher-order transfer processes, like the sequential nucleon transfer mechanisms which are in competition with the direct charge exchange reactions.

International audience; Background: An accurate description of the initial and final state interactions in the O18+Se76 collision is demanded by the NUMEN project. The study of single and double charge exchange nuclear reactions is the main purpose for NUMEN, since these can be used as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-β decay. To date, the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for the NUMEN double charge exchange studies are poorly known. The O18+Se76 case, here under study, is particularly relevant due to its connection with the Ge76 neutrinoless double-β decay.Purpose: In this work the authors want to characterize the initial-state interaction for the O18+Se76 reactions at 275 MeV incident energy determining the optical potential and evaluating the effect of couplings with the inelastic scattering on the elastic channel.Methods: The angular distributions of differential cross section were measured in the angular region between 4∘ and 22∘ in the center-of-mass reference frame. The cross sections were compared with theoretical calculations, that adopt different optical potentials. Coupling effects on the elastic channel were determined into the coupled channels formalism.Results: The excitation energy spectrum of the colliding nuclei and the cross section angular distributions were measured with satisfactory energy resolution. The elastic scattering cross section is not well reproduced in the full angular range explored when the optical model approach is adopted. A good agreement is found using coupled channel calculations. The initial state interaction for the O18+Se76 nuclear reactions at 275 MeV is determined.Conclusions: Coupled channels effects are crucial to obtain a good description of the measured elastic and inelastic channels cross sections, even at large transferred momenta where the optical model approach fails in reproducing the experimental data. The role of channel coupling could be relevant also in the analysis of other open reaction channels in the same collision and should be accounted for in double charge exchange analyses as well.