Sensitivity studies for a main $r$ process: $\beta$-decay rates

M. Mumpower, J. Cass, G. Passucci, R. Surman, A. Aprahamian

AIP Advances 4, 041009 (2014)

The pattern of isotopic abundances produced in rapid neutron capture, or $r$-process, nucleosynthesis is sensitive to the nuclear physics properties of thousands of unstable neutron-rich nuclear species that participate in the process. It has long been recognized that the some of the most influential pieces of nuclear data for $r$-process simulations are $\beta$-decay lifetimes. In light of experimental advances that have pushed measurement capabilities closer to the classic $r$-process path, we revisit the role of individual $\beta$-decay rates in the $r$ process. We perform $\beta$-decay rate sensitivity studies for a main ($A>120$) $r$ process in a range of potential astrophysical scenarios. We study the influence of individual rates during $(n,\gamma)$-$(\gamma,n)$ equilibrium and during the post-equilibrium phase where material moves back toward stability. We confirm the widely accepted view that the most important lifetimes are those of nuclei along the $r$-process path for each astrophysical scenario considered. However, we find in addition that individual $\beta$-decay rates continue to shape the final abundance pattern through the post-equilibrium phase, for as long as neutron capture competes with $\beta$ decay. Many of the lifetimes important for this phase of the $r$ process are within current or near future experimental reach.