The energy-dependence of charged particle mean multiplicity and pseudorapidity density at midrapidity measured in nucleus-nucleus and (anti)proton-proton collisions are studied in the entire available energy range. The study is performed using a model, which considers the multiparticle production process according to the dissipating energy of the participants and their types, namely a combination of the constituent quark picture together with Landau relativistic hydrodynamics. The model reveals interrelations between the variables under study measured in nucleusnucleus and nucleon-nucleon collisions. Measurements in nuclear reactions are shown to be well reproduced by the measurements in pp/pp interactions and the corresponding fits are presented. Different observations in other types of collisions are discussed in the framework of the proposed model. Predictions are made for measurements at the forthcoming LHC energies.
1.Soft hadron multiparticle production is one of the most intriguing topics in high-energy interaction studies. Data have been investigated in different types of interactions, ranging from lepton-lepton to nucleus-nucleus interactions, and over a large energy span, covering several orders of magnitude. QCD, the theory of strong interactions, has provided partonic description of many observations. However, the problem of soft multiparticle production still eludes a complete understanding and remains one of the challenging problems in high-energy physics [1]. The new high-energy data from LHC provide an opportunity to look at the system under new conditions. Of special interest are nucleusnucleus collisions, probing nuclear matter at extreme conditions, where new forms of matter are expected to be created a e-mail: sedward@mail.cern.ch b e-mail: Alexandre.Sakharov@cern.ch at very high densities and temperatures. The data available from RHIC experiments allow an interesting comparison of the particle production mechanisms with the less complex e + e − and pp systems. In this context, the global, or bulk, variables such as the average charged particle multiplicity and particle densities (spectra), which are the first available experimental observables, are of fundamental interest [1-3] as they are sensitive to the underlying interaction dynamics.In this paper we consider the center-of-mass (c.m.) energy dependence of the average multiplicity and near midrapidity density of charged hadrons produced in nucleusnucleus and (anti)proton-proton collisions. Whereas the multiplicity is sensitive mostly to the fraction of energy being transformed into observed particles in a given reaction, the midrapidity density reflects different stages of the reaction. Both variables increase with the collision c.m. energy. Recent measurements at RHIC follow the trends observed in e + e − and proton-proton interactions. The values of both bulk variables are found [4,5] to be similar when comparing the measurements in e + e − interactions at the c.m. energy of √ s ee , and in most central ("head-on") heavy-ion col...