Systematic and Statistical Uncertainties in Simulated r-Process Abundances due to Uncertain Nuclear Masses

Abstract

Unknown nuclear masses are a major source of nuclear physics uncertainty for r-process nucleosynthesis calculations. Here we examine the systematic and statistical uncertainties that arise in r-process abundance predictions due to uncertainties in the masses of nuclear species on the neutron-rich side of stability. There is a long history of examining systematic uncertainties by the application of a variety of different mass models to r-process calculations. Here we expand upon such efforts by examining six DFT mass models, where we capture the full impact of each mass model by updating the other nuclear properties-including neutron capture rates, β-decay lifetimes, and β-delayed neutron emission probabilities-that depend on the masses. Unlike systematic effects, statistical uncertainties in the r-process pattern have just begun to be explored. Here we apply a global Monte Carlo approach, starting from the latest FRDM masses and considering random mass variations within the FRDM rms error. We find in each approach that uncertain nuclear masses produce dramatic uncertainties in calculated r-process yields, which can be reduced in upcoming experimental campaigns.

Minimal nuclear energy density functional

“…At subsaturation baryon densities, 0.1n 0 < n < 0.8n 0 , conditions expected in the bottom layers of the inner crust of neutron star, there is a strong competition between the Coulomb and strong interactions, which leads to the emergence of various complex structures with similar energies that are collectively referred to [18,19] are displayed as dots. We have plotted possible r-process trajectories predicted to be realized in the case of two neutron star mergers [16,17] (red circles), in a classical hot (n, γ) ↔ (γ, n) in equilibrium r-process [170] (green circles) with the FRDM model [66] and neutron star merger with the UNEDF1 functional [74] (blue circles). With pink and green bands we display the r-process paths obtained by Mendoza-Temis et al [171] under various conditions using the FRDM model [66] and the Duflo-Zuker model [172].…”

“…The 2375 nuclear masses from [18,19] are displayed as dots. We have plotted possible r-process trajectories predicted to be realized in the case of two neutron star mergers [16,17] (red circles), in a classical hot (n, γ) ↔ (γ, n) in equilibrium r-process [170] (green circles) with the FRDM model [66] and neutron star merger with the UNEDF1 functional [74] (blue circles). With pink and green bands we display the r-process paths obtained by Mendoza-Temis et al [171] under various conditions using the FRDM model [66] and the Duflo-Zuker model [172].…”

Observations of R-Process Stars in the Milky Way and Dwarf Galaxies

“…New Experimental Facilities: Currently, theoretical calculations of r-process nucleosynthesis rely on extensive models of nuclear masses and reactions. The nuclear data uncertainties significantly limit many predictions of astrophysical r-process calculations (e.g., Eichler et al, 2015;Mendoza-Temis et al, 2015;Mumpower et al, 2016;Surman et al, 2017;Barnes et al, 2021). However, upcoming experimental facilities like the Facility for Rare Isotope Beams (FRIB), the Radioactive Isotope Beam Factor (RIBF), the International Facility for Antiproton and Ion Research (FAIR), the Advanced Rare IsotopE Laboratory (ARIEL), and the N = 126 Factory at Argonne will fundamentally transform this landscape (Horowitz et al, 2019).…”