The impact of global nuclear mass model uncertainties onr-process abundance predictions

M Mumpower,A Aprahamian,R Surman,R Schwengner,K Zuber

doi:10.1051/epjconf/20159303003

Abstract

Rapid neutron capture or ‘r -process’ nucleosynthesis may be responsible for half the production of heavy elements above iron on the periodic table. Masses are one of the most important nuclear physics ingredients that go into calculations of r -process nucleosynthesis as they enter into the calculations of reaction rates, decay rates, branching ratios and Q-values. We explore the impact of uncertainties in three nuclear mass models on r -process abundances by performing global monte carlo simulations. We show that root-mean-square (rms) errors of current mass models are large so that current r -process predictions are insufficient in predicting features found in solar residuals and in r -process enhanced metal poor stars. We conclude that the reduction of global rms errors below 100 keV will allow for more robust r -process predictions.

Highlights

The cataclysmic event(s) responsible for the production of the heaviest neutron-rich elements found in nature is referred to as the rapid neutron capture process or r process of nucleosynthesis
We explore three nuclear mass models with a range of physical assumptions: Finite Range Droplet Model (FRDM1995) [13], Duflo Zuker (DZ) [14] and HartreeFock-Bogoliubov version 17 (HFB-17) [15]
Each study was scaled to the value of Europium (Z = 63) and the same scaling applies to the average of the five halo stars; there is no observational constraint for this data point. In these studies three nuclear mass models (HFB-17, DZ, and FRDM1995) were used and nuclear masses were varied globally using the prescription defined in the previous section

Summary

Introduction

The cataclysmic event(s) responsible for the production of the heaviest neutron-rich elements found in nature is referred to as the rapid neutron capture process or r process of nucleosynthesis. Nuclear masses factor into the properties of the heaviest fissioning nuclei (e.g. barrier heights and daughter distributions) and further contribute to calculations of energy generation in astrophysical environments [2]. In this contribution we explore a new approach to assigning error bars on r-process abundance patterns from uncertain nuclear masses. Using a global monte carlo variation of all uncertain nuclear masses we create an ensemble of abundance patterns which are combined to produce the estimated error bars. An additional advantage of this new approach is that it will provide direct insight into correlations in nuclear masses

Models

Monte Carlo

Results

Conclusions