Shell-model half-lives including first-forbidden contributions for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>r</mml:mi></mml:math>-process waiting-point nuclei

Zhi, Qi‐Jun; Caurier, E.; Cuenca‐Garcìa, J. J.; Langanke, K.; Martı́nez-Pinedo, G.; Sieja, K.

doi:10.1103/physrevc.87.025803

Cited by 163 publications

(169 citation statements)

References 56 publications

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“…Importantly, these faster EDF-based half lives agree well with recent experimental data obtained for nuclei close and on the r-process path, including data for neutron-rich nuclei towards the N = 126 waiting points [28]. Here, the EDF-based half-lives, in close agreement with recent large-scale shell model calculations [29,30], point to the importance of forbidden transitions to the β decays.…”

Section: Introductionsupporting

confidence: 79%

“…At freeze-out, it corresponds to charge numbers Z ≈ 48 and Z ≈ 70, respectively. The predicted half-lives of these nuclei [29] are of the order of 100 ms which is not much less than the total duration of the r process, namely around 1 s. Changing the time the r process expends in this long-lived nuclei affects the whole dynamics of the r process and consequently impacts the r-process abundances. This timescale can be affected by modifications of individual beta-decay half-lives that so far are based on relatively uncertain theoretical approaches [49,58].…”

Section: A Time Evolution and Energy Generationmentioning

confidence: 99%

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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: Introductionsupporting

confidence: 79%

Section: A Time Evolution and Energy Generationmentioning

confidence: 99%

Nuclear robustness of therprocess in neutron-star mergers

et al. 2015

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“…The detailed expressions for the K's can be obtained from [7,8] ′ , x, x ′ and y, and for 2 − just one matrix element z is involved. The expressions for these matrix elements are given in [7].…”

Section: Theory Of β-Decaymentioning

confidence: 99%

Effect of first-forbidden decays on the shape of neutrino spectra

Fang

Brown

2015

Phys. Rev. C

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We examine the effect of First Forbidden (FF) decays on β-decay neutrino spectra by performing microscopic nuclear structure calculations. By analyzing the FF decay branches of even-even nuclei we conclude that FF decays may be responsible for part of the missing neutrinos in the so called "Reactor Neutrino Anomaly". Further calculations and more experimental data are needed for a firm conclusion.

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“…There are experimental indications (Domingo-Pardo et al 2013;Kurtukian-Nieto et al 2014;Morales et al 2014) that the half-lives of nuclei around N = 126 are shorter than predicted by the FRDM+QRPA approach (Möller et al 2003). Several theoretical calculations based on an improved treatment of forbidden transitions suggest a similar behavior (Suzuki et al 2012;Zhi et al 2013). Caballero et al (2014) have explored the impact on r-process calculations utilizing the halflive predictions of Borzov (2011).…”

Section: β-Decay Rates Of the Heaviest Nuclei And Their Relation To Tmentioning

confidence: 94%

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

Eichler¹,

Arcones²,

Kelić³

et al. 2015

ApJ

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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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Shell-model half-lives including first-forbidden contributions forr-process waiting-point nuclei

Cited by 163 publications

References 56 publications

Nuclear robustness of therprocess in neutron-star mergers

Nuclear robustness of therprocess in neutron-star mergers

Effect of first-forbidden decays on the shape of neutrino spectra

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

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