Probing the density dependence of nuclear symmetry energy through isospin transport in heavy-ion reactions

TL;DR

This paper reviews recent experimental and theoretical progress in constraining the nuclear symmetry energy's density dependence using isospin transport in heavy-ion reactions, with implications for nuclear physics and astrophysics.

Contribution

It synthesizes recent advancements and provides constraints on the symmetry energy using isospin diffusion data and transport models, aiding future studies of dense nuclear matter.

Findings

Confidence regions for symmetry energy derived from isospin transport ratios.

Use of state-of-the-art nuclear functionals in constraining the symmetry energy.

Highlights from INDRA-FAZIA collaboration data and BUU model calculations.

Abstract

The density dependence of the nuclear symmetry energy remains one of the key uncertainties in contemporary nuclear physics, with significant implications for the structure of exotic nuclei, the dynamics of heavy-ion collisions, and the properties of astrophysical objects such as neutron stars and core-collapse supernovae. However, extracting robust constraints requires observables that are minimally affected by final-state interactions and are reliably predicted by transport models. This review synthesizes recent theoretical and experimental advancements in constraining the symmetry energy by leveraging isospin diffusion in heavy-ion reactions within the Fermi energy domain. Recent results from the INDRA-FAZIA collaboration, including isospin transport ratio data, and Boltzmann-Uehling-Uhlenbeck (BUU) transport model calculations are highlighted. Confidence regions for the symmetry energy are extracted from isospin transport ratios and isospin diffusion currents by utilizing state-of-the-art nuclear functionals, including both ab initio and phenomenological approaches, with a particular focus on the density regions probed by these experiments. The resulting constraints will aid future Bayesian studies of the nuclear equation of state and contribute to a more unified understanding of dense matter in both terrestrial experiments and astrophysical environments.