Session Y12: Nuclear Astrophysics III

Calculation of Stellar NucleosynthesisAbundances using ENDF/B-VIII.0 andTENDL-2015 Evaluated Nuclear Data Libraries

Evaluated Nuclear Data File (ENDF) libraries contain complete
collections of reaction cross sections, fission
yields and decay data. These data collections have been used worldwide
in the nuclear industry and national security applications. The recently released
evaluated libraries were explored for nuclear astrophysics purposes
and findings analyzed.
Maxwellian-averaged cross sections (MACS) and astrophysical reaction
rates were calculated using the ENDF/B-VIII.0 and Talys Evaluated
Nuclear Data Library (TENDL) data sets. The calculated cross sections
were combined with the solar system abundances and fitted using the
classical model of stellar nucleosynthesis. Astrophysical abundances for
rapid- and slow-neutron capture, r- and s-processes, respectively, were
extracted from the present data and compared with available values. The
current results demonstrate the large potential of evaluated libraries and
mutually-beneficial relations between the nuclear industry and research
efforts.   

Influence of statistical uncertainties of Skyrme-type nuclear mass models on r-process nucleosynthesis simulations

Nuclear models play a critical role in attempts to study the formation of heavy elements via the rapid neutron capture (r-) process of nucleosynthesis. We examine the influence of statistical uncertainties in the parameters of one nuclear model, the Skyrme-type energy density functional UNEDF1, on r-process nucleosynthesis simulations by sampling 50 points within the Bayesian posterior distribution of the model's parameters. We calculate nuclear masses and corresponding nuclear capture, decay, and fission properties for each sample to perform nucleosynthesis simulations across a range of astrophysical r-process conditions and report the corresponding ranges in abundance patterns. We forecast improvements to Skyrme-type nuclear models that may occur in response to possible future experiments at the Facility for Rare Isotope Beams, and we quantify the resulting reduction of uncertainties in r-process simulations. Finally, we discuss correlations between parameters of Skyrme-type nuclear models and specific features of r-process abundance patterns. We discuss possible implications of these correlations.   

Beta-Decay Experiment for Rapid Neutron-Capture Process Nucleosynthesis

The rapid neutron capture process (r-process) is a nucleosynthesis process responsible for about half of the abundances of elements heavier than iron in the universe. Its astrophysical site is not uniquely identified. The observation of elemental abundances in halo stars shows a good agreement with solar system r-process abundances for Z≥52, but not for the lighter elements 38≤Z≤47. There might be another nucleosynthesis process, for example the weak r-process, which produces medium mass neutron-capture elements around Zr. The recently observed kilonovae after the detection of the neutron star merger event GW170817 provides strong evidence that this is a site of the r-process. However, we need more nuclear and astronomical data to identify the site of weak r-process. In this work, the β-decay half-lives and β-delayed neutron emission probability (P_n) of neutron-rich isotopes in the region of mass A = 100 have been measured. The experiment was performed in the Radioactive Ion Beam Factory (RIBF) at RIKEN in Japan, in 2017. Thanks to the state-of-the-art instrumentation of the β-delayed neutron detector at RIKEN (BRIKEN), we will be able to provide P_n values of very short-lived isotopes for the first time.