Symmetry Energy of Dilute Warm Nuclear Matter

TLDR

The symmetry energy of nuclear matter, essential for exotic nuclei, heavy‑ion collisions, and astrophysics, is inadequately described by mean‑field models at low temperature and density where correlations and bound states dominate. The study aims to extract free and internal symmetry energies at subsaturation densities and temperatures below 10 MeV using new heavy‑ion collision data. A quantum‑statistical model incorporating cluster formation accurately reproduces experimental symmetry energies and unifies the low‑density limit with quasiparticle approaches near saturation.

Abstract

The symmetry energy of nuclear matter is a fundamental ingredient in the investigation of exotic nuclei, heavy-ion collisions and astrophysical phenomena. New data from heavy-ion collisions can be used to extract the free symmetry energy and the internal symmetry energy at subsaturation densities and temperatures below 10 MeV. Conventional theoretical calculations of the symmetry energy based on mean-field approaches fail to give the correct low-temperature, low-density limit that is governed by correlations, in particular by the appearance of bound states. A recently developed quantum statistical (QS) approach that takes the formation of clusters into account predicts symmetry energies that are in very good agreement with the experimental data. A consistent description of the symmetry energy is given that joins the correct low-density limit with quasiparticle approaches valid near the saturation density.