The Nuclear Matter Symmetry Energy at $0.03\leq \rho/\rho_0\leq 0.2$
  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. 
R. Wada, K. Hagel, L. Qin, J. B. Natowitz, G. R\"opke, S. Shlomo, A.   Bonasera, S. Typel, Z. Chen, M. Huang, J. Wang, H. Zh...
nucl-ex