Central collisions of relativistic heavy ions

The energy spectra of protons and light nuclei produced by the interaction of ⁴He and ²⁰Ne 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° and 150°, 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 ¹²C and ²⁰Ne 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 U(²⁰Ne,X), E=250 MeV/nucl.; U(²⁰Ne,X), U(α,X) E=400 MeV/nucl.; U(²⁰Ne,X), Al(²⁰Ne,X), E=2.1 GeV/nucl.; measured σ(E,θ), X=p, d, t, ³He,⁴He. U(²⁰Ne,X), U(α,X), E=400 MeV/nucl.; U(²⁰Ne,X), E=2.1 GeV/nucl.; measured σ(E, θ), Li to O. U(²⁰Ne,X), U(¹²C,X), E=2.1 GeV/nucl.; measured σ(E, 90°), ⁴He to B. Nuclear fireballs, coalescence, thermodynamics of light nuclei production.