Transverse Momentum And Multiplicity Distributions Of Final-State Products In High Energy Collisions

In the 1970s, Tsung-Dao Lee et al. predicted that a new state of matter, namely, quark-gluon plasma (QGP) can be created in relativistic heavy-ion (nucleus-nucleus) collisions due to high temperature and high density. This prediction makes the field of high-energy collisions to be developed very rapidity. Many physical researchers devote themselves to the work of exploring the production mechanisms of particles and masses. To get more useful information of QGP is always an important goal of modern nuclear physics. For a short lifetime, the interacting mechanisms of the QGP created in heavy-ion collisions must be deduced by the final-state observable quantities. So there are many phenomenological models to be established to describe nucleus-nucleus collisions at high energies.In this thesis, we have studied the transverse momentum and multiplicity distributions of final-state products (particles and fragments) in high energy collisions. The main work can be divided into three main chapters.Firstly, we have analyzed the transverse momentum distributions of final-state particles in high energy collisions in the framework of multisource thermal model. In the model, many sources produced in collisions are divided into a few groups due to different interaction mechanisms or event samples. The multi-component Erlang distribution can be obtained by the weight sum of Erlang distribution which is the folding results of many exponential distributions. First of all, we have used the multi-component Erlang distribution not only describing the transverse momentum distributions in proton-proton (pp), proton-(deuteron)-nucleus [p(d)A], and nucleus-nucleus (AA) collisions but also analyzing the transverse momentum distributions contributed by the soft excitation process and hard scattering process in a unified description in p-Pb and Pb-Pb collisions. We have obtained the relationships between the mean transverse momentum (<pT>) and the center-of-mass energy, <pT> and particle mass, as well as <pT> and rapidity. Meanwhile, the connections between the number of emission sources or effective participant partons (n) and rapidity, n and particle mass, as well as n and centrality are investigated. In high energy nuclear collisions, the contribution ratio of hard process is less than that of the soft process.At the same time, we have compared the two-component Boltzmann distribution and the Tsallis statistics of particle transverse momentum in pp, p-Vb, and Pb-Pb collisions at LHC energies. We have found that the results of two distributions are in agreement with the experiment data of the ALICE and LHCb Collaborations. In the calculation, there are 3+2 free parameters. The two-component Boltzmann distribution contains three parameters, two temperatures (T1 and T2) and one probability (k1). The two temperatures reflect the temperature fluctuation of interacting system. The Tsallis distribution includes two parameters, temperature (T) and non-equilibrium degree (q). The temperature describes the temperature fluctuation of the system. To see clearly the connection of the temperature parameters from different distributions, we have described the particle transverse momentums in heavy-ion collisions at RHIC and LHC energies by (two-) Boltzmann distribution and (two-) Tsallis distribution, and extracted the effective Boltzmann temperature and Tsallis temperature. We can see the linear relation between the Tsallis temperature and Boltzmann temperature.Secondly, in order to obtain more information on interacting mechanisms of nucleus-nucleus collisions and production processes of final-state particles, we have studied the multiplicity distribution of final-state particles. In the begining, the dependences of final-state particle rapidity and participant contribution ratio on the center-of-mass energy in a wide energy range are studied. A new method which measures the speed of sound is provided. Based on combining the revised Landau hydrodynamic model and the participant-spectator model, we have analyzed the pseudorapidity distribution of charged particles in proton-proton or proton-antiproton collisions. The combined model can be bringed into the framework of multisource thermal model. The calculated results are in agreement with the experiment data of some collaborations. We have extracted the square speed of sound from the width of pseudorapidity distribution, and the result is in agreement with those of hadron resonance gas model and lattice quantum chromodynamics theory. Next, the production cross-sections of projectile-like isotopes in 112Sn+112Sn and 124Sn+124Sn reactions are studied in the framework of multisource thermal model. In the treatment of isotope, the neutron number can be regard as the multiplicity-like of neutrons. The production cross-section distribution is directly proportional to the multiplicity-like of neutrons. We would like to point out that our model can describe the experiment data and the fitting parameters can be explained.Finally, we have analyzed the transverse momentum and pseudorapidity distributions of charged particles in heavy ion collisions at high energy by using the revised multisource thermal model. The contribution ratios of leading target nucleons, target cylinder, projectile cylinder, and leading projectile nucleons in different regions in the rapidity space are obtained. Meanwhile, the rapidity distributions of charged particles are given by the fitting parameters from the transverse momentum and pseudorapidity distributions. The spatial shapes of interacting events in different spaces and different centralities are presented. These spatial shapes provide intuitionisticly pictures of particle distributions at the stage of kinetic freeze-out.