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 NN s =200 GeV and by ALICE Collaboration at CERN-LHC in Pb-Pb collisions at NN s =2.76 TeV. The theoretical results are well consistent with experimental data.

By taking into account the effects of leading particles, we discuss the pseudorapidity distributions of the charged particles produced in high energy heavy ion collisions in the context of evolution-dominated hydrodynamic model. The leading particles are supposed to have a Gaussian rapidity distribution normalized to 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 NN s =200 GeV and by ALICE Collaboration at CERN-LHC in Pb-Pb collisions at NN s =2.76 TeV. PACS number(s): 25.75.Ag, 25.75.Ld, 24.10.Nz

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Using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of produced charged particles in high energy heavy ion collisions. As usual, the leading particles here mean the particles which inherit the quantum numbers of colliding nucleons and carry off most parts of the incident energy. We argue that the rapidity distributions of leading particles have the Gaussian form with the normalization constant being equal to the number of participants. We find that the results from the hydrodynamic model alone are not consistent with the experimental data carried out by BNL-RHIC-PHOBOS Collaboration in Au + Au collisions at √ s NN = 200 GeV. Only after the contributions from leading particles are included, can the experimental measurements be described well.

In the context of combined model of evolution-dominated hydrodynamics + leading particles, we discuss the pseudorapidity distributions of charged particles produced in p-p collisions. A comparison is made between the theoretical predictions and experimental measurements. The combined model works well in p-p collisions in the whole available energy region from s =23.6 to 900 GeV.