Neutron Emission in Relativistic Nuclear Collisions

Previously reported differences between the measured proton and neutron energy spectra for the reaction ∼400 MeV/nucleon ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$+$\mathrm{U}\to p$,$n+X$ are discussed. A parameter-free cascade-coalescence model of heavy-ion collisions is shown to account for these differences. Such measurements are shown to be sensitive to the degree of projectile-target equilibration in relativistic nuclear collisions.