Effect of medium dependent binding energies on inferring the temperatures and freeze-out density of disassembling hot nuclear matter from cluster yields

We explore the abundance of light clusters in asymmetric nuclear matter at subsaturation density. With increasing density, binding energies and wave functions are modified due to medium effects. The method of Albergo, Costa, Costanzo, and Rubbino (ACCR) for determining the temperature and free nucleon density of a disassembling hot nuclear source from fragment yields is modified to include, in addition to Coulomb effects and flow, also effects of medium modifications of cluster properties, which become of importance when the nuclear matter density is above ${10}^{-3}\hspace{0.5em}{\mathrm{fm}}^{-3}$. We show how the analysis of cluster yields, to infer temperature and nucleon densities, is modified if the shifts in binding energies of in medium clusters are included. Although, at low densities, the temperature calculated from given yields changes only modestly if medium effects are taken into account, larger discrepancies are observed when the nucleon densities are determined from measured yields.

Figure 1

The ratio between the ACCR temperature $T^{(a)}$ (no medium effects) and $T$ (including medium effects) as a function of the baryon density $n_B=n_p+n_n$ for various values of $T$.

Figure 2

Similar to that described in the caption to Fig. 1 but for the ratio $n_B^{(a)}/n_B$.