Background: Reaction mechanisms involved in charge-exchange reactions are heavily mixed. From an experimental perspective, separating the role of specific mechanisms from others is impossible due to quantum interference. To address this, rigorous theoretical studies must be applied. Refining the used quantum states is a key factor, not only for this purpose but also for reactions involving weak interactions, such as neutrinoless double-beta decay. Purpose: The present study investigates the Ca40(O18,F18)K40 reaction at an energy of 275 MeV. It is assumed that the reaction primarily proceeds through three mechanisms: direct meson exchange (DME), nucleon transfer - first a neutron, then a proton (n-p) - and the reverse (p-n). The main goal of the study is to compare the experimental data with the calculations for this reaction and to investigate the role of the different mechanisms in a coherent and consistent manner. Methods: For the direct process, the distorted-wave Born approximation (DWBA) method was employed. The two-step DWBA procedure is used for the n-p and p-n mechanisms. In these calculations, the semi-microscopic optical potential is utilized, validated through comparisons of calculated cross sections for elastic, inelastic, and single-nucleon transfer channels with experimental data. Calculations to obtain information about nuclear structure, spectroscopic amplitudes, and onebody transition densities were performed using the large-scale shell model, employing a unified p-sd model space for projectile nuclei and an sd-pf model space for target nuclei. Results: The ground state and the first ten excited states for both the target and projectile nuclei were included in the calculations. The differential cross sections, calculated considering three mechanisms, were compared with the experimental data across three available excitation energy regions of interest. Conclusion: The differential cross-sections obtained using the DWBA method, considering the three mechanisms, show good agreement with the available experimental data. This result can be interpreted as evidence for the applicability of the nuclear-reaction and nuclear-structure models adopted in the present study. In particular the DME mechanism gives the dominant contribution to the cross section, indicating that the experimental conditions of the present work in terms of projectile/ejectile combination, incident energy, and explored angles are favorable to highlight the role of the direct meson-exchange mechanism.
Direct and two-step processes in the 275MeVCa40(O18,F18)K40 reaction within a unified model
A. Spatafora;F. Cappuzzello;D. Carbone;M. Cavallaro;M. Colonna;
2025-01-01
Abstract
Background: Reaction mechanisms involved in charge-exchange reactions are heavily mixed. From an experimental perspective, separating the role of specific mechanisms from others is impossible due to quantum interference. To address this, rigorous theoretical studies must be applied. Refining the used quantum states is a key factor, not only for this purpose but also for reactions involving weak interactions, such as neutrinoless double-beta decay. Purpose: The present study investigates the Ca40(O18,F18)K40 reaction at an energy of 275 MeV. It is assumed that the reaction primarily proceeds through three mechanisms: direct meson exchange (DME), nucleon transfer - first a neutron, then a proton (n-p) - and the reverse (p-n). The main goal of the study is to compare the experimental data with the calculations for this reaction and to investigate the role of the different mechanisms in a coherent and consistent manner. Methods: For the direct process, the distorted-wave Born approximation (DWBA) method was employed. The two-step DWBA procedure is used for the n-p and p-n mechanisms. In these calculations, the semi-microscopic optical potential is utilized, validated through comparisons of calculated cross sections for elastic, inelastic, and single-nucleon transfer channels with experimental data. Calculations to obtain information about nuclear structure, spectroscopic amplitudes, and onebody transition densities were performed using the large-scale shell model, employing a unified p-sd model space for projectile nuclei and an sd-pf model space for target nuclei. Results: The ground state and the first ten excited states for both the target and projectile nuclei were included in the calculations. The differential cross sections, calculated considering three mechanisms, were compared with the experimental data across three available excitation energy regions of interest. Conclusion: The differential cross-sections obtained using the DWBA method, considering the three mechanisms, show good agreement with the available experimental data. This result can be interpreted as evidence for the applicability of the nuclear-reaction and nuclear-structure models adopted in the present study. In particular the DME mechanism gives the dominant contribution to the cross section, indicating that the experimental conditions of the present work in terms of projectile/ejectile combination, incident energy, and explored angles are favorable to highlight the role of the direct meson-exchange mechanism.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
