Impact of nuclear masses on r -process nucleosynthesis: Bulk properties versus shell effects

We investigate the impact of the model estimating the masses of exotic nuclei on <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>r</a:mi> </a:math> -process nucleosynthesis, assessing the dependence of the abundance distribution on the specific properties of nuclear masses. By decomposing theoretical nuclear mass predictions into a liquid-drop parametrization and local shell effects, we show that <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mi>r</b:mi> </b:math> -process abundances are virtually insensitive to large variations of the masses, which originate from nuclear bulk properties of the model, such as the symmetry energy. In contrast, the mass component associated with local shell effects is the main driver of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mi>r</c:mi> </c:math> -process abundance variations, despite its relatively minor contribution to the absolute value of neutron separation energies. Our work suggests that experimental and theoretical studies of masses devoted to <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mi>r</d:mi> </d:math> -process applications, such as the nucleosynthesis in the ejecta of neutron star mergers, should focus on the physical origin and determination of local changes in mass trends.