Comparing symmetry energy predictions and recent constraints from the ASY-EOS experiment at GSI

Predictions for the interaction part of the symmetry energy obtained from microscopic approaches based upon different foundations are reviewed and discussed in the light of recent updated constraints obtained from reaction observables in the ASY-EOS experiment at GSI. The discussion is then extended to the neutron skin thickness in ${}^{208}\mathrm{Pb}$ and its relation to the density derivatives of the symmetry energy at and below saturation density. With regard to the latter, the main point is to demonstrate the importance of proper consideration of the theoretical uncertainties of microscopic predictions in order to guide phenomenological analyses.

Figure 1

The EoS of symmetric matter (left side) and of neutron matter (right side) for the theories and models considered in this study.

Figure 2

As in Fig. 1, but for the symmetry energy.

Figure 3

Microscopic predictions of the interaction part of the symmetry energy at ${\mathrm{N}}^2\mathrm{LO}$ and ${\mathrm{N}}^3\mathrm{LO}$ of chiral perturbation theory, and corresponding power-law fits. See inset for the definition of the various curves.

Figure 4

Left: The potential part of the symmetry energy as predicted with the DBHF calculation compared with a power-law fit. Right: The same, but for the APR model [27].

Figure 5

Microscopic predictions of the interaction part of the symmetry energy at ${\mathrm{N}}^3\mathrm{LO}$ with EFT truncation error. The shaded area shows the empirical constraint from Ref. [12].

Figure 6

Relation between the $L$ parameter and the neutron skin in ${}^{208}\mathrm{Pb}$. Blue shaded area: empirical constraint for $L$ and corresponding constraint for the neutron skin. Green area: predictions from Table 3. Equation (14) produces the pink region.