Speaker
Description
The rapid neutron-capture process (or r-process) is responsible for the production of about half of the elements heavier than iron in the Universe and
is expected to take place in neutron star mergers and possibly in exploding
massive stars. To estimate the composition of the ejecta, a reaction network
involving about 6000 neutron-rich nuclei with all reactions of interest needs
to be calculated. The major nuclear transmutations include neutron captures,
photoneutron emissions, beta-decays as well as fission processes. Since mass
differences set the energy scale in all nuclear reactions, nuclear binding energies
are crucial ingredients to estimate reaction rates. For the r-process in particular, mass differences govern the competition between neutron capture and
photoneutron emission. Unfortunately, only about 2500 nuclear masses have
been measured so far. Since experimental efforts have so far not been able to
access the neutron-rich nuclei produced by the r-process during the neutron
irradiation, theoretical predictions are fundamental to fill the gap.
Models built on energy density functionals (EDF) have been successful pro-
viding a microscopic description of the atomic nucleus at a reasonable numerical
cost. Over the last five years, the state-of-the-art BSkG (Brussels-Skyrme-on-a-
Grid) family of Skyrme-EDF parametrizations has been developed. These mod-
els go beyond the usual limitations of traditional Skyrme-EDF parametrizations
by accounting for highly complex nuclear shapes through symmetry breaking
during their adjustment. Starting with BSkG3 [1], they have been fitted to all
known masses, as well as to actinide fission barriers and infinite nuclear mat-
ter properties. This allows these models to accurately predict nuclear masses,
with root-mean-square deviations of about 0.63 MeV, making them some of the
best mass models available. During the last year, a significant number of developments have been made. On the one hand, our latest model, BSkG5 [2],
has marked the first time that a Skyrme N2LO parametrization has been able
to reproduce nuclear masses with root-mean-square deviations below 0.7 MeV.
On the other hand, large-scale calculations of fission barriers and spontaneous-
fission half-lives have been performed with BSkG3 [3], yielding the most accurate
results obtained so far by any microscopic method.
In this talk, I will present our latest mass model, BSkG6. This new model,
also based on the Skyrme N2LO functional, incorporates new microscopic dynamical terms that provide a better description of beyond-mean-field contributions to the binding energy while maintaining a moderate computational cost.
[1] G. Grams, W. Ryssens, G. Scamps, S. Goriely, and N. Chamel, “Skyrme-
Hartree-Fock-Bogoliubov mass models on a 3D mesh: III. From atomic
nuclei to neutron stars”, The European Physical Journal A 59, 270 (2023).
[2] G. Grams et al., “Skyrme-hartree-fock-bogoliubov mass models on a 3d
mesh: v. the n2lo extension of the skyrme edf”, arXiv preprint arXiv:2601.05968
(2026).
[3] A. Sánchez-Fernández, S. Bara, W. Ryssens, and S. Goriely, “Accurate spontaneous fission half-lives from a microscopic large-scale nuclear structure model”, Physics Letters B, 140287 (2026).