Recent measurements of preequilibrium neutron and proton transverse emission from ${}^{112,124}\mathrm{Sn}+{}^{112,124}\mathrm{Sn}$ reactions at $50\mathrm{MeV}/A$ have been completed at the National Superconducting Cyclotron Laboratory. Free nucleon transverse emission ratios are compared to those of $A=3$ mirror nuclei. Comparisons are made to Boltzmann-Uehling-Uhlenbeck (BUU) transport calculations and conclusions concerning the density dependence of the asymmetry term of the nuclear equation of state at subnuclear densities are made. Comparison to BUU model predictions indicate a density dependence of the asymmetry energy that is closer to a form in which the asymmetry energy increases as the square root of the density for the density region studied. A coalescent-invariant analysis is introduced as a means of reducing suggested difficulties with cluster emission in total nucleon emission.

• Received 20 February 2006

DOI:https://doi.org/10.1103/PhysRevLett.97.052701