  The charged particles produced in heavy ion collisions consist of two parts:
One is from the freeze-out of hot and dense matter formed in collisions. The
other is from the leading particles. In this paper, the hot and dense matter is
assumed to expand according to the hydrodynamic model including phase
transition and decouples into particles via the prescription of Cooper-Frye.
The leading particles are as usual supposed to have Gaussian rapidity
distributions with the number equaling that of participants. The investigations
of this paper show that, unlike low energy situations, the leading particles
are essential in describing the pseudorapidity distributions of charged
particles produced in high energy heavy ion collisions. This might be due to
the different transparencies of nuclei at different energies.
