Systematic Study Of Pseudorapidity Distribution Of Final-State Particles In High Energy Collisions

High energy collisions are one of the most important topics in modern particle and nuclear physics research. A lot of problems can be explained through the study of high-energy collisions, such as quark-gluon plasma (QGP), Higgs boson in standard model, and particle generation mechanism. Scientists think that the QGP exists in early universe after transient tens of microseconds of Big Bang, when the state of matter is under in the high temperature and energy density conditions. When its energy density is low enough, it changes to the normal state of matter. Many countries and organizations have built some high-energy accelerators or colliders, such as the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), for high energy physics research. Through high energy collisions, we can study the nature of the particles and interaction theory predicted by the Standard Model, and other theories such as the supersymmetry theory proposed by physicists. High energy collisions can also give answers to many other questions.We can get important information about the mechanism of particle generation and the system evolution formed in high-energy collisions from a variety of global observables. Pseudorapidity, multiplicity and transverse momentum distributions are commonly used as research objects. They are also the quantities of the "first-day" measurements in experiments. Pseudorapidity distribution is of great significance to research QGP. In this dissertation, we study systematically pseudorapidity distributions of charged particles produced in p-p or p-p, Cu-Cu and Pb-Pb collisions in different ways, as well as other distributions obtained according to pseudorapidity distribution in high-energy p-p collisions. In addition, we do primary research on transverse momentum spectrums of μ- produced in d-Au collisions.According to the multi-source thermal model (previously the multi-source ideal gas model), the present work analyzes pseudorapidity distributions of charged particles produced in p-p or p-p, Cu-Cu and Pb-Pb collisions at different energies. The calculations show that the multi-source thermal model can describe well the pseudorapidity distributions of charged particles produced in these collisions. Firstly, based on the pseudorapidity distributions of charged particles produced in p-p or p-p collisions at different energies reported by the UA5, UA1, P238, CDF, ALICE and CMS Collaborations, the parameter values are obtained from the modelling analyzes on the data. We find different relationships between different parameters and logarithmic center-of-mass energy. The pseudorapidity distributions of charged particles produced in p-p or p-p collisions at the higher LHC energies are speculated by these relationships. Secondly, based on the pseudorapidity distributions of charged particles produced in Cu-Cu collisions at (?)sNN-=22.4,62.4 and 200 GeV obtained at the BNL RHIC, the model calculation shows that the contributions of leading nucleons increase with the increasing impact parameter, the cylinder length (the longitudinal shift of the interacting system) in rapidity space increases with the increasing energy and does not depend on centrality at a given energy. Thirdly, the pseudopapidity distributions of charged particles produced in Pb-Pb collisions at (?)sNN-=2.76 TeV measured by the ATLAS, ALICE and CMS Collaborations at CERN LHC are analyzed by the model. The parameter values indicate that the rapidity shifts of the interacting system are almost independent of the centrality class. The contribution of leading nucleons increases with the increasing centrality (percentage) class.In the final state of the collisions, there are a lot of massive particles. We have improved the multi-source thermal model to relativistic situation. The experimental data of UA5, UA1, P238, CDF, ALICE and CMS Collaborations are analyzed again by the model. The calculated results are found to be in agreement with the experimental data. Our calculated results show that the improved multi-source thermal model (the relativistic multi-source thermal model) can describe well the pseudorapidity distributions of charged particles produced in p-p or p-p collisions over a center-of-mass energy range from 0.053 to 7 TeV.We have improved the relativistic multi-source thermal model to Landau hydromechanics situation. The particle transverse momentum spectrum is considered to obey Boltzmann distribution and the projectile (target) cylinder length in rapidity space is taken to be the revised width of rapidity distribution in Landau’s hydrodynamical model. The re-improved model describes the pseudorapidity distributions by using only two parameters, a rapidity shift and a normalization constant. We analyze the pseudorapidity distributions of charged massive particles by this re-improved model (the multi-source thermal model with Landau hydromechanics). It is found that the calculated results are in agreement with the experimental data of p-p or p-p collisions at energies available at the past and present colliders.Considering the correlations of many physical quantities, based on the (pseudo)rapidity distribution of final-state particles produced in p-p collisions at high energy, the probability distributions of momentums, longitudinal momentums, transverse momentums (transverse masses), energies, velocities, longitudinal velocities, transverse velocities, and emission angles of the considered particles are obtained in the framework of the multi-source thermal model. The number density distributions of particles in coordinate and momentum spaces and related transverse planes, the particle dispersion plots in longitudinal and transverse coordinate space, and the particle dispersion plots in transverse momentum plane at the stage of freeze out in high energy p-p collisions are also obtained.Based on transverse momentum spectrums of μ-produced in d-Au collisions reported by the RHIC PHENIX Collaboration, we analyze the experimental data by using the multi-source thermal model. It is found that the calculated results are in agreement with the experimental data, it is show that the model can describe well the transverse momentum distribution of μ-produced in d-Au collisions at (?)SNN-=200 GeV. It is shown that the changing trends of the parameters in backward and forward rapidity ranges are obviously different.