Thermodynamic Quantities Of High-energy Nuclear Collision Systems Based On Statistical Analysis

The high-energy nuclear collision is one of the crucial research topics in particle physics and nuclear physics.By high-energy nuclear collisions,we can study the structure of matter,the properties of QGP,the evolution of the universe and so on.In the experiment,different high-energy accelerators were built.RHIC and LHC have successfully launched a new era in the study of high-energy nuclear collisions.The detector can measure various hadrons produced in collisions,but it is difficult to measure the whole process of the matter evolution in the collision system.The transverse momentum spectrum and multiplicity of particles produced in collisions are important observations in the investigation of the highenergy collision system.By studying the natural of particles produced,we can analyze the information of matter evolution,the mechanism of particle production and so on.In the theoretical research,some thermodynamic statistical models have been applied,such as Boltzmann statistical model,Tsallis statistical model,Boltzmann-Gibbs blast-wave model,Tsallis blast-wave model and so on.Based on these models,several modified methods have been proposed.These theoretical models can help us to better comprehend the properties of different collision systems.In the framework of statistical model,properties of the particle distribution and thermodynamic quantities of the high energy collision system are analyzed and discussed in this work,which are divided mainly into the following two parts.In the first part,the participant quark model(or contributor quark model)is introduced.Combined with the modified Tsallis-Pareto-type function(TP-like function),we study the transverse momentum distributions of charged hadrons for different collision centralities in nuclear collisions at different collision energies,which are Au+Au collisions at(?)=7.7—62.4 GeV,130 and 200 GeV,Cu+Cu collisions at(?)=62.4 GeV and 200 GeV,Pb+Pb collisions at(?)=2.76 TeV and 5.02 TeV,Xe+Xe collisions at(?)=5.44 TeV.The model results are compared with the experimental results in detail.The temperature T,the power index n and the modifying factor a_o are obtained.The modifying factor a_o is not 1 and does not change obviously with different collision centralities.It is proved that the modified method of the model is practicable.Moreover,it is shown that the temperature is related positively to the collision centralities,and the particle system will deviate gradually from the equilibrium state at the high energy.These properties are helpful to understand further the production of particles in high-energy nuclear collisions.In the second part,the non-extensive parameter q is introduced into Bolzmann-Gibbs entropy.The Tsallis non-extensive statistical distribution function which can meet the thermodynamic consistency is used to describe the pT of different particles produced in Au+Au collisions at(?)=7.7,11.5,19.6 and 39 GeV.These particles include K_s~0,φ,Λ,(?),(?)~+,(?)~-,(?)~+ and Ω~-.It is found that the model can well describe the transverse momentum spectra for different collision centralities.The temperature T and the non-extensive parameter q are obtained by a comparison between model results and experimental data.Based on this analysis,we calculate the related thermodynamic quantities like the specific heat C_v,the conformal symmetry breaking measure (?)-3P/T~4,the squared speed of sound c_s~2.For different collision centralities,the behaviors of these quantities are discussed.It is shown that the temperature,specific heat,conformal symmetry breaking measure and squared speed of sound are getting smaller from the central collision(0%—5%)to the peripheral collision(60%—80%).In the central collision,more particles participate in the collision than the peripheral collision,the motion is more vigorous and the excitation degree of the system is higher.