Charged-particle rapidity density in Au+Au collisions in a quark   combination model
  Rapidity/seudorapidity densities for charged particles and their centrality, rapidity and energy dependence in Au+Au collisions at RHIC are studied in a quark combination model. Using a Gaussian-type rapidity distribution for constituent quarks as a result of Landau hydrodynamic evolution, the data at $\sqrt{s_{NN}}=130, 200$ GeV at various centralities in full pseudorapidity range are well described, and the charged particle multiplicity are reproduced as functions of the number of participants. The energy dependence of the shape of the $dN_{ch}/d\eta$ distribution is also described at various collision energies $\sqrt{s_{NN}}=200, 130, 62.4$ GeV in central collisions with same value of parameters except 19.6 GeV. The calculated rapidity distributions and yields for the charged pions and kaons in central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV are compared with experimental data of the BRAHMS Collaboration. 
Feng-lan Shao, Tao Yao and Qu-bing Xie