Baryon distribution in relativistic heavy-ion collisions

Recently there is considerable interest in highly relativistic heavy-ion collisions which was suggested as a way to produce a phase transition from the ordinary confined matter to the unconfined quark-gluon plasma. As the fraction of baryons in the early universe was small, it seems desirable to design a heavy-ion collider such that when the energy density in the central rapidity is high enough for a phase transition, there is no net baryon density there. Recent investigations reveal that the average downward shift of the projectile baryon rapidity is quite large. The formation of a pure quark-gluon plasma depends on the shape of the baryon momentum distributions. It is of interest to estimate the baryon momentum distribution. The baryon distribution is studied using the Glauber-type multiple collision model. Results indicate that in the energy range of √s/A approx. 10-100 GeV, it is difficult to form a pure quark-gluon plasma in the mid-rapidity region without a baryon impurity of a few percent (in energy density). Increasing the collider energy brings some improvement to the degree of baryon impurity. However, by nature of the skew distributions due to multiple inelastic collisions, some baryon impurity remains