Constraining the density dependence of the symmetry energy: the isospin transport ratio revisited

TL;DR

This paper revisits the isospin transport ratio in nuclear reactions to better constrain the density dependence of the symmetry energy, demonstrating its sensitivity to key isovector parameters and its potential to discriminate between models affecting neutron star predictions.

Contribution

The study refines the isospin transport ratio analysis, enhancing the comparison between experimental data and theoretical models to reduce uncertainties in symmetry energy parameters.

Findings

Isospin transport ratios are sensitive to $E_{sym}$, $L_{sym}$, and $K_{sym}$.

Realistic equation of state models can be discriminated using isospin diffusion experiments.

Precise measurement of neutron-to-proton ratio is crucial for model discrimination.

Abstract

The isospin diffusion of the quasi-projectile formed in the $^{64,58}Ni$ on $^{64,58}Ni$ reactions in the Fermi energy domain is investigated in the framework of the Boltzmann-Uehling-Uhlenbeck transport model. The well known isospin transport ratio observable is revisited, with the aim of insuring an optimal comparison between experimental data and theoretical calculations and reducing the present uncertainties in the extraction of empirical equation of state parameters. We show that isospin transport ratios are sensitive to all the low order isovector parameters ($E_{sym}$, $L_{sym}$ and $K_{sym}$). We demonstrate that realistic models of the equation of state, covering the uncertainty that presently affects the theoretical description of neutron stars static observables, can be effectively discriminated by isospin diffusion experiments, provided the neutron to proton ratio of the projectile remnant is precisely measured as a function of centrality.