Towards more accurate and reliable predictions for nuclear applications

Goriely, Stéphane

doi:10.1140/epja/i2015-15172-2

Cited by 56 publications

(86 citation statements)

References 120 publications

(40 reference statements)

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“…These include both fission barriers and collective inertial masses. Recent global calculations [81][82][83] have mainly focussed on the description of fission barriers neglecting the important role of collective masses that are normally described using a simple phenomenological prescription [84] in rprocess applications. Furthermore, it is important to address the impact of dynamical versus static descriptions of fission observables [85,86] Beta-decay half-lives have not been consistently computed with the mass models explored in this work.…”

Section: Discussionmentioning

confidence: 99%

Nuclear robustness of therprocess in neutron-star mergers

et al. 2015

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We have performed r-process calculations for matter ejected dynamically in neutron star mergers based on a complete set of trajectories from a three-dimensional relativistic smoothed particle hydrodynamic simulation with a total ejected mass of ∼ 1.7 × 10 −3 M . Our calculations consider an extended nuclear network, including spontaneous, β-and neutron-induced fission and adopting fission yield distributions from the ABLA code. In particular we have studied the sensitivity of the r-process abundances to nuclear masses by using different models. Most of the trajectories, corresponding to 90% of the ejected mass, follow a relatively slow expansion allowing for all neutrons to be captured. The resulting abundances are very similar to each other and reproduce the general features of the observed r-process abundance (the second and third peaks, the rare-earth peak and the lead peak) for all mass models as they are mainly determined by the fission yields. We find distinct differences in the predictions of the mass models at and just above the third peak, which can be traced back to different predictions of neutron separation energies for r-process nuclei around neutron number N = 130. In all simulations, we find that the second peak around A ∼ 130 is produced by the fission yields of the material that piles up in nuclei with A 250 due to the substantially longer beta-decay half-lives found in this region. The third peak around A ∼ 195 is generated in a competition between neutron captures and β decays during r-process freeze-out. The remaining trajectories, which contribute 10% by mass to the total integrated abundances, follow such a fast expansion that the r process does not use all the neutrons. This also leads to a larger variation of abundances among trajectories as fission does not dominate the r-process dynamics. The resulting abundances are in between those associated to the r and s processes. The total integrated abundances are dominated by contributions from the slow abundances and hence reproduce the general features of the observed r-process abundances. We find that at timescales of weeks relevant for kilonova light curve calculations, the abundance of actinides is larger than the one of lanthanides. This means that actinides can be even more important than lanthanides to determine the photon opacities under kilonova conditions. Moreover, we confirm that the amount of unused neutrons may be large enough to give rise to another observational signature powered by their decay.

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Section: Discussionmentioning

confidence: 99%

Nuclear robustness of therprocess in neutron-star mergers

et al. 2015

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“…We also follow the decay back to stability during the r-process freeze-out and the competition between late neutron captures and neutron release by fission and β-decays of heavy nuclei (see similar discussions of freeze-out effects without including fission in Mumpower et al 2012 and the references therein). Late neutron captures have a direct effect on the final position of the third r-process peak (also seen in Goriely et al 2013 andGoriely 2015). To study the dependence of the final abundance distribution on the freeze-out characteristics, we pick a typical trajectory from the same database of trajectories 11 that was used in Korobkin et al (2012).…”

Section: Introductionmentioning

confidence: 99%

THE ROLE OF FISSION IN NEUTRON STAR MERGERS AND ITS IMPACT ON THEr-PROCESS PEAKS

Eichler¹,

Arcones²,

Kelić³

et al. 2015

ApJ

185

165

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Comparing observational abundance features with nucleosynthesis predictions of stellar evolution or explosion simulations, we can scrutinize two aspects: (a) the conditions in the astrophysical production site and (b) the quality of the nuclear physics input utilized. We test the abundance features of r-process nucleosynthesis calculations for the dynamical ejecta of neutron star merger simulations based on three different nuclear mass models: The Finite Range Droplet Model, the (quenched version of the) Extended Thomas Fermi Model with Strutinsky Integral, and the Hartree-Fock-Bogoliubov mass model. We make use of corresponding fission barrier heights and compare the impact of four different fission fragment distribution models on the final r-process abundance distribution. In particular, we explore the abundance distribution in the second r-process peak and the rare-earth sub-peak as a function of mass models and fission fragment distributions, as well as the origin of a shift in the third r-process peak position. The latter has been noticed in a number of merger nucleosynthesis predictions. We show that the shift occurs during the r-process freeze-out when neutron captures and β-decays compete and an (n,γ)-(γ,n) equilibrium is no longer maintained. During this phase neutrons originate mainly from fission of material above A = 240. We also investigate the role of β-decay half-lives from recent theoretical advances, which lead either to a smaller amount of fissioning nuclei during freeze-out or a faster (and thus earlier) release of fission neutrons, which can (partially) prevent this shift and has an impact on the second and rare-earth peak as well.

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“…It also remains of first importance to estimate the statistical as well as systematic uncertainties affecting the predictions far away from the experimentally known region. Such a difficult task has been started regarding mass predictions [17], but remains to be performed for the reaction as well as β-decay rates. Our capacity to predict the fundamental nuclear ingredients for reaction models, namely nuclear masses, optical potentials, γ-ray strength functions, nuclear level densities, fission barriers, as well as the predictive power of the reaction and β-decay models are discussed in Ref.…”

Section: Nuclear Physicsmentioning

confidence: 99%

“…Our capacity to predict the fundamental nuclear ingredients for reaction models, namely nuclear masses, optical potentials, γ-ray strength functions, nuclear level densities, fission barriers, as well as the predictive power of the reaction and β-decay models are discussed in Ref. [17].…”

Section: Nuclear Physicsmentioning

confidence: 99%

Ther-process nucleosynthesis and related challenges

et al. 2017

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Abstract. The rapid neutron-capture process, or r-process, is known to be of fundamental importance for explaining the origin of approximately half of the A > 60 stable nuclei observed in nature. Recently, special attention has been paid to neutron star (NS) mergers following the confirmation by hydrodynamic simulations that a non-negligible amount of matter can be ejected and by nucleosynthesis calculations combined with the predicted astrophysical event rate that such a site can account for the majority of r-material in our Galaxy. We show here that the combined contribution of both the dynamical (prompt) ejecta expelled during binary NS or NS-black hole (BH) mergers and the neutrino and viscously driven outflows generated during the post-merger remnant evolution of relic BH-torus systems can lead to the production of r-process elements from mass number A > ∼ 90 up to actinides. The corresponding abundance distribution is found to reproduce the solar distribution extremely well. It can also account for the elemental distributions observed in low-metallicity stars. However, major uncertainties still affect our understanding of the composition of the ejected matter. These concern (i) the β-interactions of electron (anti)neutrinos with free neutrons and protons, as well as their inverse reactions, which may affect the neutron-richness of the matter at the early phase of the ejection, and (ii) the nuclear physics of exotic neutron-rich nuclei, including nuclear structure as well as nuclear interaction properties, which impact the calculated abundance distribution. Both aspects are discussed in the light of recent hydrodynamical simulations of NS mergers and microscopic calculations of nuclear decay and reaction probabilities.

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Towards more accurate and reliable predictions for nuclear applications

Cited by 56 publications

References 120 publications

Nuclear robustness of therprocess in neutron-star mergers

Nuclear robustness of therprocess in neutron-star mergers

THE ROLE OF FISSION IN NEUTRON STAR MERGERS AND ITS IMPACT ON THEr-PROCESS PEAKS

Ther-process nucleosynthesis and related challenges

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