r-Process Nucleosynthesis with Ab Initio Nuclear Masses around the N=82 Shell Closure.

Our understanding of the origin of heavy elements beyond iron relies on the rapid neutron capture process (r process), which accounts for roughly half of their cosmic abundance. However, the extreme neutron-rich conditions required for the r process involve many nuclei that remain experimentally inaccessible, making theoretical predictions essential. We explore the impact of nuclear masses calculated with the ab initio valence-space in-medium similarity renormalization group, focusing on the region around the N=82 shell closure. We show for the first time that such ab initio mass calculations can be used to refine r-process predictions compared to global, but more phenomenological mass models. With the ab initio masses, the waiting point of the second r-process peak is strengthened, which leads to an overall slower nucleosynthesis flow, lower abundances of nuclei beyond the peak, and a stronger shift of the third r-process peak.