Exploratory study on the masses of odd-$Z$ nuclei and $r$-process simulation based on the deformed relativistic Hartree-Bogoliubov theory in continuum (2503.09324v1)

Abstract: \textbf{Background:} Nuclear masses of exotic nuclei are important for both nuclear physics and astrophysics. The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) is capable of providing proper descriptions for exotic nuclei by simultaneously including deformation and continuum effects. The mass table of even-$Z$ nuclei with $8\le Z\le 120$ has been established based on the DRHBc theory [ADNDT 158, 101661 (2024)]. \textbf{Purpose:} This work aims to systematically estimate the masses of odd-$Z$ nuclei based on the available DRHBc results of even-$Z$ nuclei, thereby providing a pseudo DRHBc mass table for all nuclei with $8\le Z\le 120$. This mass table can then be employed in the $r$-process studies to investigate the influence of deformation on $r$-process. \textbf{Method:} The mass of an odd nucleus is expressed as a function of the masses and odd-even mass differences of its neighboring even nuclei, with the odd-even mass difference approximated by the average pairing gap. The $r$-process simulations are carried out using the site-independent classical $r$-process model based on the waiting-point approximation. \textbf{Results and Conclusions:} The approximation of the odd-even mass difference with the average pairing gap is validated to be effective, by reproducing the masses of even-$Z$ odd-$N$ nuclei calculated by DRHBc. Combining the DRHBc masses of even-$Z$ nuclei and the estimated masses of odd-$Z$, a pseudo DRHBc mass table is established, with the root-mean-square (rms) deviation from available mass data $\sigma=1.50$ MeV. This pseudo DRHBc mass table is applied to the $r$-process simulation, and the impact of nuclear deformation effects is analyzed. The deformation effects can influence the $r$-process path and thus affect the $r$-process abundance. In particular, the nuclear shape transitions can even lead to the discontinuity of the $r$-process path.