The Nuclear Matter Symmetry Energy at $0.03\leq \rho/\rho_0\leq 0.2$

TL;DR

This study extends measurements of the symmetry energy in low-density nuclear matter using experimental data from nuclear collisions, finding good agreement with quantum statistical models and providing new empirical constraints.

Contribution

It provides new experimental data on the density dependence of symmetry energy at low densities, using thermal coalescence models and multi-detector measurements.

Findings

Symmetry energy coefficients agree with quantum statistical model calculations.

Densities sampled range from 0.03 to 0.2 times saturation density.

Temperatures in the range 5 to 10 MeV were studied.

Abstract

Measurements of the density dependence of the free symmetry energy in low density clustered matter have been extended using the NIMROD multi-detector at Texas A&M University. Thermal coalescence models were employed to extract densities, $\rho$, and temperatures, $T$, for evolving systems formed in collisions of 47 $A$ MeV $^{40}$Ar + $^{112}$Sn,$^{124}$Sn and $^{64}$Zn + $^{112}$Sn, $^{124}$Sn. Densities of $0.03 \leq \rho/\rho_0 \leq 0.2$ and temperatures in the range 5 to 10 MeV have been sampled. The free symmetry energy coefficients are found to be in good agreement with values calculated using a quantum statistical model. Values of the corresponding symmetry energy coefficient are derived from the data using entropies derived from the model.