  The charged particles produced in nucleus-nucleus collisions are classified
into two parts,One is from the hot and dense matter created in collisions. The
other is from leading particles. The hot and dense matter is assumed to expand
and generate particles according to BJP hydrodynamics, a theory put forward by
A. Bialas, R. A. Janik and R. Peschanski. The leading particles are argued to
possess a Gaussian rapidity distribution with the normalization constant
equaling the number of participants. A comparison is made between the
theoretical results and the experimental measurements performed by BRAHMS and
PHOBOS Collaboration at BNL-RHIC in Au-Au and Cu-Cu collisions at
sqrt(s_NN)=200 GeV and by ALICE Collaboration at CERN-LHC in Pb-Pb collisions
at sqrt(s_NN) =2.76 TeV. The theoretical results are well consistent with
experimental data.
