Thu·Oct 21, 2021Thursday·October 21, 2021

1. 01*

   Analysis of two-nucleon transfer reactions in the 20Ne + 116Cd system at 306 MeV

   D. Carbone🇮🇹 · J. L. Ferreira🇧🇷 · S. Calabrese🇮🇹 · F. Cappuzzello🇮🇹 · M. Cavallaro🇮🇹 · A. Hacisalihoglu🇹🇷 · H. Lenske🇩🇪 · J. Lubian🇧🇷 · R. I. Magana Vsevolodovna🇮🇹 · E. Santopinto🇮🇹 · C. Agodi🇮🇹 · L. Acosta🇲🇽 and 37 other authors

   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 São 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.

   nucl-exnucl-thPRC(2020)·54 citations
2. 02*

   Study of one-proton transfer reaction for the ${}^{18}$O + ${}^{48}$Ti system at 275 MeV

   O. Sgouros🇮🇹 · M. Cavallaro🇮🇹 · F. Cappuzzello🇮🇹 · D. Carbone🇮🇹 · C. Agodi🇮🇹 · A. Gargano🇮🇹 · G. De Gregorio🇮🇹 · C. Altana🇮🇹 · G. A. Brischetto🇮🇹 · S. Burrello🇩🇪 · S. Calabrese🇮🇹 · D. Calvo🇮🇹 and 29 other authors

   Single-nucleon transfer reactions are processes that selectively probe single-particle components of the populated many-body nuclear states. In this context, recent efforts have been made to build a unified description of the rich nuclear spectroscopy accessible in heavy-ion collisions. An example of this multichannel approach is the study of the competition between successive nucleon transfer and charge exchange reactions, the latter being of particular interest in the context of single and double beta decay studies. To this extent, the one-proton pickup reaction ${}^{48}$Ti(${}^{18}$O,${}^{19}$F)${}^{47}$Sc at 275 MeV was measured for the first time, under the NUMEN experimental campaign. Differential cross-section angular distribution measurements for the ${}^{19}$F ejectiles were performed at INFN-LNS in Catania by using the MAGNEX large acceptance magnetic spectrometer. The data were analyzed within the distorted-wave and coupled-channels Born approximation frameworks. The initial and final-state interactions were described adopting the São Paulo potential, whereas the spectroscopic amplitudes for the projectile and target overlaps were derived from shell-model calculations. The theoretical cross sections are found to be in very good agreement with the experimental data, suggesting the validity of the optical potentials and the shell-model description of the involved nuclear states within the adopted model space.

   nucl-exnucl-thPRC(2021)·41 citations
3. 03*

   Nuclear data evaluation with Bayesian networks

   Georg Schnabel🇦🇹 · Roberto Capote🇦🇹 · Arjan Koning🇦🇹 · David Brown

   Bayesian networks are graphical models to represent the probabilistic relationships between variables in the Bayesian framework. The knowledge of all variables can be updated using new information about some of the variables. We show that relying on the Bayesian network interpretation enables large scale inference and gives flexibility in incorporating prior assumptions and constraints into the nuclear data evaluation process, such as sum rules and the non-negativity of cross sections. The latter constraint is accounted for by a non-linear transformation and therefore we also discuss inference in Bayesian networks with non-linear relationships. Using Bayesian networks, the evaluation process yields detailed information, such as posterior estimates and uncertainties of all statistical and systematic errors. We also elaborate on a sparse Gaussian process construction compatible with the Bayesian network framework that can for instance be used as prior on energy-dependent model parameters, model deficiencies and energy-dependent systematic errors of experiments. We present three proof-of-concept examples that emerged in the context of the neutron data standards project and in the ongoing international evaluation efforts of ${}^{56}$Fe. In the first example we demonstrate the modelization and explicit estimation of relative energy-dependent error components of experimental datasets. Then we show an example evaluation using the outlined Gaussian process construction in an evaluation of ${}^{56}$Fe in the energy range between one and two MeV, where R-Matrix and nuclear model fits are difficult. Finally, we present a model-based evaluation of ${}^{56}$Fe between 5 MeV and 30 MeV with a sound treatment of model deficiencies. The R scripts to reproduce the Bayesian network examples and the nucdataBaynet package for Bayesian network modeling and inference have been made publicly available.

   ↳ physics.data-annucl-exnucl-th3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.