Speed of Sound Parameter from RHIC and LHC Heavy-Ion Data

In framework of combing the participant-spectator model and the Landau hydrodynamic model, the pseudorapidity distributions of charged particles produced in heavy-ion (or nucleus-nucleus) collisions at RHIC and LHC energies are described by a modified Landau hydrodynamic model, where the Landau hydrodynamic model is applied to the target/projectile spectators and the target/projectile participants, respectively. The modeling results are in agreement with the PHOBOS and ALICE experimental data. Then, the values of square speed of sound (cs2) for the participants and spectators can be obtained from the widths of charged particle pseudorapidity distributions. Some features of cs2 for different centralities and center-of-mass energies are obtained too.