Event Patterns Extracted From Particle Spectra At Stage Of Kinetic Freeze-out In High Energy Collisions

High energy particle-particle,particle-nucleus,and nucleus-nucleus collisions are one of major and importrant aspects in particle and nuclear physics.The success of the Relativistic Heavy Ion Collider(RHIC)and the Large Hadron Collider(LHC)has opened up a new epoch for high energy nucleus-nucleus(heavy ion)collisions,and is the only way to study the evolution of the universe in experiments at present.The collisions at the RHIC and LHC provide excellent environments and conditions of high temperature and density,in which not only abundant phenomena in multiparticle productions are produced,but also the quark-gluon plasma(QGP)is created.Theoretically,phenomenological models are a main method to study the process of high energy collisions at prensent.By analyzing various properties of final-state particles is an important method to restore the original process of collisions in high energy nuclear physics.In terms of models and methods,this thesis mainly bases on the multisource thermal model and the Landau hydrodynamic model,and uses the thermal and statistical methods to analyze the collisions.To understand the whole interacting system as minutely as possible,the event reconstruction and reappearance method is used in the modelling analyses.By using this method,we can partly obtain the event patterns or particle scatter plots at the stage of kinetic freeze-out of interacting system.Generally,the event patterns are expected to be different in descriptions for different particles produced in different collisions at different energies.To reconstruct and reappear the event patterns at kinetic freeze-out,we need at least the spectra in transverse plane(vertical to the beam direction)and longitudinal direction(the same as the beam direction).The distribution of particles in the transverse plane can be described by the transverse momentum,and that in longitudinal direction can be described by the(pseudo)rapidity.Many functions can be used to describe the transverse momentum(pT)spectrum,which include,but are not limited to,the standard distribution,Tsallis statistics,Erlang distribution,inverse power-law,and so forth.Among these functions,some of them(standard distribution,Tsallis statistics,and Erlang distribution)are based on thermal or statistical reason,and other(inverse power-law)is based on the quantum chromodynamic(QCD)calculus.Generally,the spectrum in the low-pT region is described by the thermal and statistical distributions,and the spectrum in the high-pT region is described by the QCD calculus.In most cases,one needs a two-component distribution to describe the whole pT spectrum.To describe the rapidity spectrum,one has the Gaussian distribution,two-Gaussian distribution,three-Gaussian distributions,and other modelling descriptions such as the three-fireball model and the model with two Tsallis(or Boltzmann-Gibbs)clusters of fireballs.The Gaussian rapidity distribution is resulted from the Landau hydrodynamic model and its revisions.Most models describe the rapidity spectrum by an arithmetic solution rather than an analytic one.Based on the descriptions of transverse momentum and(pseudo)rapidity spectra,we can use the Monte Carlo method to extract some discrete values of transverse momentum and(pseudo)rapidity.Other quantities such as velocity,energy,velocity compoents,and momentum components can also be obtained according to some definitions and assumptions.Then,we can construct the particle scatter plots or event patterns in three-dimensional spaces.In terms of the analyses of particle spectra and event patterns,this thesis contains three main aspects.Firstly,in the framework of multisource thermal model,we analyze the transverse momentum and rapidity spectra of net-baryons(baryons minus antibaryons)produced in central gold-gold(Au-Au)collisions at the center-of-mass energies per nucleon pair of 62.4 and 200 GeV,measured by the BRAHMS Collaboration at the RHIC.Each source in the model is described by the Tsallis statistics.The effective temperature(T)and entropy index(q)from the transverse momentum spectrum and the parameters related to the rapidity shif and contribution ratio(k)of each source from the rapidity spectrum are extracted.Then,the four types of parameters are used to structure some scatter plots of the considered particles in some three-dimensional spaces at the stage of kinetic freeze-out,which are expected to show different characteristics for different particles and processes.The related methodology can be used in the analyses of particle production and event holography,which are useful for us to better understand the heavy ion collisions and particle interactions.The second aspect of this thesis is that the transverse momentum and pseudorapidity spectra of Z bosons,quarkoniumstates(some charmonium cc mesons such as J/ψ and ψ(2S)and some bottomonium bb mesons such as γ(1S),γ(2S),and γ(3S)),and charged particles produced in proton-proton(p-p)collisions at the center-of-mass energies of 2.76 and 7 TeV and in lead-lead(Pb-Pb)collisions at the center-of-mass energy per nucleon pair of 2.76 TeV,measured by the ALICE,LHCb,CMS and ATLAS Collaboration at the LHC,are analyzed by a hybrid model.In the model,the transverse momentum spectrum is described by a two-component distribution which contains the Erlang distribution or Tsallis statistics and the inverse power-law.The(pseudo)rapidity spectrum is described by a one-component or more-component Landau hydrodynamic model,such as the two-component Gaussian distribution.Based on the parameters extracted from the transverse momentum and pseudorapidity spectra,the Monte Carlo metbod is used to simulate particle distributions in different spaces.In addition,we analyze the spectra of charged particles produced in p-p and Pb-Pb collisions at 2.76 TeV measured by the ATLAS Collaboration at the LHC.The transverse momentum spectra of charged particles produced in p-p collisions and Pb-Pb collisions with different centralities,the transverse momentum spectra of charged particles measured in different pseudorapidity ranges,and the pseudorapidity spectra of charged particles measured in diffeent transverse momentum intervals are compared,and the characteristics of the related parameters are obtained.Furthermore,we analyze the elliptic flow and the dependence of elliptic flow on transverse momentum of charged particles produced in Pb-Pb collisions at 2.76 TeV for different centralities,measured by the ATLAS Collaboration at the LHC.At the same time,the model results of transverse momentum spectra and dependence of elliptic flow on transverse momentum for π++π-,K+ + K-,and p+p in the same collisions are obtained.The third aspect of this thesis is that the characteristics of π-mesons produced in different types of collisions at different energies in the Beam Energy Scan(BES)Program at the Super Proton Synchrotron(SPS),measured by the NA61/SHINE and NA49 Collaboration,are analyzed.The Standard distribution(Boltzmann distribution)is used to analyze the transverse momentum spectra of π-mesons produced in different rapidity ranges in inelastic p-p interactions at incident beam momenta of 20,31,40,80,and 158 GeV/c,and to extract the effective temperature and the tendency of parameters.We use a two-component Landau Hydrodynamic model to describe the rapidity spectra.The model results are in agreement with the experimental data.Based on the analyses,the fine event patterns in some three-dimensional spaces are extracted and compared with the non-fine event patterns extracted from the transverse mass and rapidity spectra.Using the same method,the transverse mass and rapidity spectra of π-mesons produced in p-p,beryllium-beryllium(Be-Be),argon-scandium(Ar-Sc),and Pb-Pb collisions are analyzed and the dependences of parameters on incident energy and nuclear radius are investigated.Then,the scatter plots ofπ-mesons,which reflect the event patterns,are structured in three-dimensional spaces.By comparing the model results with the transverse momentum(mass)and(pseudo)rapidity spectra measured by different collaborations at different colliders and accelerator,one can see that the model results are approximately in agreement with the experimental data within errors.By using the different thermal and statistical functions to describe the experimental data can also verify the rationality and flexibility of our model.Based on the descriptions of transverse momentum(mass)and(pseudo)rapidity spectra,we can extract the event patternss of different particles at the stage of kinetic freeze-out in different spaces.Generally,the event patterns are expected to depend mainly on particle type and collision energy.In particular,in three-dimensional velocity space,the event patterns of light flavor particles show a rough sphericity or a fat ellipsoid along beam direction.In the sphericity,the number density distribution of particles depends on collision energy and the highest density closes to βz= 1.The event patterns of heavy flavor particles show a rough cylinder,and are expected to have a different number density feature.The fact that light and heavy flavor particles have different event patterns render that they are produced by different mechanisms and at different stages in collision process.Although the anisotropic spectra are obvious in some cases,the effect on the transverse momentum spectra and the event patterns is not obvious.There are obvious differences between the fine event patterns and non-fine event patterns of π-mesons produced at BES energies.We can neglect the influence of elliptic flow,and have to consider the fine spectra,in the extractions of parameter values and event patterns.