Determine the neutron skin thickness and nuclear symmetry energy at relativistic heavy ion collisions
Abstract
Nuclear symmetry energy and its density dependence are crucial for understanding of the masses and drip lines of neutron-rich nuclei and the equation of state of nuclear and neutron star matter. Neutron skin thickness has traditionally been measured using low-energy electron and hadron scatterings from nuclei. In this brief review, we summarize recent progress in determining the neutron skin thickness and the nuclear symmetry energy density slope parameter in an unconventional way by using relativistic isobar (^96Ru+^96Ru and ^96Zr+^96Zr) collisions. The final-state observables of relativistic heavy ion collisions can reflect the initial collision geometry of the collision, but in a way sensitive to the final-state evolution. Since the effects of final-state evolution are nearly identical between isobar collisions, the differences in the final-state observables directly reflect the nuclear structure difference of the colliding nuclei. Thus, isobar collisions provide an excellent platform for measuring the nuclear structure independent of unresolved details of the strong interaction. We start by laying out the importance of nuclear structure in relativistic isobar collisions. We then present and discuss several isobar ratio observables to measure the neutron skin thicknesses of the isobars and the nuclear symmetry energy density slope parameter, namely, ratios in the charged hadron multiplicity, mean transverse momentum, net charge multiplicity, dilepton photoproduction rate, and flow anisotropies.
