Baryon distribution in relativistic heavy-ion collisions

In order to determine whether a pure quark-gluon plasma with no net baryon density can be formed in the central rapidity region in relativistic heavy-ion collisions, we estimate the baryon distribution by using a Glauber-type multiple-collision model in which the nucleons of one nucleus degrade in energy as they make collisions with nucleons in the other nucleus. As a test of this model, we study first nucleon-nucleus collisions at 100 GeV/c and compare the theoretical results with the experimental data of Barton et.al The results are then generalized to study the baryon distribution in nucleus-nucleus collisions. It is found that in the head-on collision of two heavy nuclei ($A\gtrsim 100$), the baryon rapidity distributions have broad peaks and extend well into the central rapidity region. The energy density of the baryon in the central rapidity region is about 5-6% of the total energy density at a center-of-mass energy of 30 GeV per nucleon and decreases to about 2-3% at a center-of-mass energy of 100 GeV per nucleon. The stopping power for a baryon in nuclear matter is extracted.