Temperatures Extracted From Transverse Momentum Spectra And Their Dependence On Centrality In High Energy Collisions

One of the most major and astonishing aspects in particle and nuclear physics is high energy particle-particle,particle-nuclues and nuleus-nuleus(AA)collisions.It was early in 1970's,when T.D.Lee et al.predicted a new and very hot and dense state of matter called Quark-Gluon Plasma(QGP)in relativistic heavy ion(or AA)collisions.Both the relativistic heavy ion collider(RHIC)and large hadron collider(LHC)provide some good opportunities to study the characteristics of QGP,and final state products.Furthermore,the STAR Collaboration at RHIC has been performing the beam energy scan(BES)program in order to search for the expected possible critical energy at which the phase transition from hadronic matter to QGP occurs in high energy AA collisions and the transverse momentum(pT)spectra of particles is an important quantity to be measured in the collisions.The study of pT spectra of particles can give some useful information about(but not limited to)the effective temperature(Teff),initial temperature(Ti),kinetic freeze-out temperature(To),kinetic freeze-out volume(V)of the interacting system,and transverse flow velocity(?T)of the final state particles.The characteristic of transverse excitation and dynamical expansion of the interacting system can be understood by the detailed study of the temperature of interacting system and transverse flow velocity of the final state particles and the former is mainly related to the soft excitation process,which can provide a better understanding of the excitation degree of the interacting system in high energy regions.Various hydrodynamic models and thermal and statistical models have been introduced and used in high energy collisions.The former describes mainly the system evolution and focuses on the dynamic behavior of multiple particles,while the properties of produced particles are mainly described by the later and it focuses on the collective or global statistical behavior of the final state particles.These models describe partly interacting process and its products,and they could supply each other.In this thesis we study the PT spectra of different final state particles produced at RHIC and LHC energies in different collision systems.We extract Teff,Ti,To,V and ?T from pT spectra of particles by using the blast-wave model with Boltzmann-Gibbs statistics,the Hagedorn thermal model and the standard distribution.This thesis contains three main aspects in terms of the analysis of particles spectra and the extractions of parameters.Firstly,the pT spectra of different types of particles produced in the mid-rapidity interval in gold-gold(Au-Au),deuteron-gold(d-Au)and proton-proton(pp)collisions at RHIC energies((?)GeV),lead-lead(Pb-Pb),proton-lead(p-Pb)and pp collisions at LHC energies((?)=2.76 TeV,(?)and(?)=7 TeV respectively)are conformably and approximately described by the blast-wave model with Boltzmann-Gibbs statistics.The dependence of To and ?T on centrality and rest mass is obtained.Both To and ?T are observed to be larger in central collisions than in peripheral collisions and reveals the scenario for multiple kinetic freeze-outs because T0 is mass dependent.We analyzed the behavior of To,?T,mean PT(<pT>)and Ti extracted from the PT spectra of charged particles(?-,K-and anti-p)at different centralities in Au-Au and Pb-Pb collisions at 200 GeV and 2.76 TeV respectively,and they increase with the increasing centrality,it is noteworthy that Ti is obtained by(?).We also analyzed the PT spectra of ?+,K+and p at BES energies and observed an increasing trend of To,?T,<pT>and Ti with the increasing energy and centrality.Secondly,we analyzed the pT spectra of charged particles(n+,K+and p or ?+ +?-,K+ +K-and p+anti-p)in Au-Au,d-Au,Pb-Pb and p-Pb collisions by the Hagedorn thermal model and the standard distribution in terms of multi-component.The Teff extracted from the PT spectra is larger in the central collisions than in the peripheral collisions.In the linear relation between Teff and particle rest mass,the intercept is regarded as To.It is shown that Ti is larger than Teff and the later is larger than To and all these temperatures in central collisions are comparable to those in peripheral collisions and at the LHC are comparable with those at the RHIC.Thirdly,the PT spectra of ?-,K-and anti-p produced in central and peripheral Au-Au andpp collisions at RHIC at-62.4 GeV,as well as in central and peripheral Pb-Pb and pp collisions at LHC at(?)=5.02 TeV have been analyzed by the standard distribution in terms of multi-component.The Teff and V are extracted from the PT spectra and it shows a methodical behavior with the mass dependence for different particles which indicates to an early freeze out of the heavy particles.Mass dependent differential kinetic freeze-out scenario(the scenario for multiple kinetic freeze-outs)is also observed because of different V for emissions of different particles.Furthermore,the extracted thermodynamic parameters for peripheral AA and pp collisions at the same are almost equivalent.In the extraction of Teff and V from the PT spectra of ?-,K-and anti-p in different centrality intervals in Au-Au and Pb-Pb collisions at 200 GeV and 2.76 TeV respectively,the intercept in the linear relation between Teff and rest mass of particle is considered as To,while the slope in the linear relation between<pT>and mean moving mass is regarded as ?T.We observed that all these quantities increase with the increase of centrality due to the fact that<pT>increase with increasing the centrality and it indicates the larger momentum(energy)transfer and further multiple-scattering happens in central centrality.