Effect of a density isomer on high-energy heavy-ion collisions

On the basis of conventional nuclear fluid dynamics, we study the sensitivity of high-energy heavy-ion collisions to a density isomer in the nuclear equation of state, as well as to a variation in the nuclear compressibility coefficient. Our equation of state is a new functional form which has the property that the speed of sound approaches the speed of light in the limit of infinite compression. The equations of relativistic nuclear fluid dynamics are solved numerically in three spatial dimensions by use of a particle-in-cell finite-difference computing method for the reaction ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ + ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ at a laboratory bombarding energy per nucleon of 393 MeV. By integrating over the appropriate ranges of impact parameter, we compute the double-differential cross section $\frac{d^2\sigma }{\mathrm{dEd}\Omega }$ corresponding both to all impact parameters and to central collisions constituting 15% of the total cross section. To within numerical uncertainties, the results for the various equations of state are very similar to one another except for central collisions at laboratory angle $\theta =30\mathrm{}°$ and for both central collisions and all impact parameters at $\theta =150\mathrm{}°$. In these cases, over certain ranges of energy, $\frac{d^2\sigma }{\mathrm{dEd}\Omega }$ is larger for the density isomer than for conventional equations of state. The results calculated for all impact parameters are compared with the experimental data of Sandoval et al. for outgoing charged particles.