Central collisions of relativistic heavy ions

The energy spectra of protons and light nuclei produced by the interaction of $^{4}\mathrm{He}$ and $^{20}\mathrm{Ne}$ projectiles with Al and U targets have been investigated at incident energies ranging from 0.25 to 2.1 GeV per nucleon. Single fragment inclusive spectra have been obtained at angles between 25\ifmmode^\circ\else\textdegree\fi{} and 150\ifmmode^\circ\else\textdegree\fi{}, in the energy range from 30 to 150 MeV/nucleon. The multiplicity of intermediate and high energy charged particles was determined in coincidence with the measured fragments. In a separate study, fragment spectra were obtained in the evaporation energy range from $^{12}\mathrm{C}$ and $^{20}\mathrm{Ne}$ bombardment of uranium. We observe structureless, exponentially decaying spectra throughout the range of studied fragment masses. There is evidence for two major classes of fragments; one with emission at intermediate temperature from a system moving slowly in the lab frame, and the other with high temperature emission from a system propagating at a velocity intermediate between target and projectile. The high energy proton spectra are fairly well reproduced by a nuclear fireball model based on simple geometrical, kinematical, and statistical assumptions. Light cluster emission is also discussed in the framework of statistical models.NUCLEAR REACTIONS $\mathrm{U}(^{20}\mathrm{Ne},X)$, $E=250$ MeV/nucl.; $U(^{20}\mathrm{Ne},X)$, $U(\ensuremath{\alpha},X)$ $E=400$ MeV/nucl.; $\mathrm{U}(^{20}\mathrm{Ne},X)$, $\mathrm{Al}(^{20}\mathrm{Ne},X)$, $E=2.1$ GeV/nucl.; measured $\ensuremath{\sigma}(E,\ensuremath{\theta})$, $X=p,d,t,^{3}\mathrm{He},^{4}\mathrm{He}$. $\mathrm{U}(^{20}\mathrm{Ne},X)$, $U(\ensuremath{\alpha},X)$, $E=400$ MeV/nucl.; $U(^{20}\mathrm{Ne},X)$, $E=2.1$ GeV/nucl.; measured $\ensuremath{\sigma}(E,\ensuremath{\theta})$, Li to O. $\mathrm{U}(^{20}\mathrm{Ne},X)$, $U(^{12}\mathrm{C},X)$, $E=2.1$ GeV/nucl.; measured $\ensuremath{\sigma}(E,90\ifmmode^\circ\else\textdegree\fi{})$, $^{4}\mathrm{He}$ to B. Nuclear fireballs, coalescence, thermodynamics of light nuclei production.