Analyses Of Two-and Three-pion Interferometry In AMPT Model

Detecting the space-time information of particle-emitting source is an important research issure in high-energy nucleus-nucleus collision experiments,and pion interferometry analysis is an effective method to obtain the space-time structure of the systems produced in high-energy collisions.A multi-phase transport model(AMPT model)is mature to simulate the nucleus-nucleus collisions at the Relativistic Heavy Ion Collider(RHIC)and the Large Hadron Collider(LHC)energies.The thesis research object is to study the two-and three-pion interferometry for the particle-emitting sources produced in high-energy nucleus-nucleus collisions simulated by AMPT model.In Chapter 1,the developments of high-energy nucleus-nucleus collision physics,the main evolution stages of collision system and the developments of pion interferometry are briefly introduced.Chapter 2 describes the theory of two-pion interferometry,three-pion interferometry formulas and AMPT model.On this basis,the two-and three-pion interfer-ometry analyses are performed in Chapter 3 and Chapter 4,respectively,for the high-energy nucleus-nucleus collision events simulated by the string-dissolved version of AMPT model.In Chapter 3,we study the variation of two-pion correlation function with the freeze-out time and the transverse-momentum of the pion mesons.The influences of impact parameter and resonance decay on two-pion correlation function are investigated.In Chapter 4,we study the dependences of three-pion correlation function and pure three-pion correlation function on pi-on momentum and collision energy.The influences of impact parameter and resonance decay on three-pion correlation function are examined.We also investigate normalized three-pion correlation factor.The thesis researches indicate that the two-pion correlations of the pions freezed out early are stronger which correspond to the sources with smaller size.The two-and three-pion correlation functions increase with increasing pion momentum,for the particle-emitting sources in relativistic nucleus-nucleus collisions simulated by AMPT model.This reflects there is a correlation between the particle emission points and momentum for the expanding sources.The values of two-and three-pion correlation functions become a little larger when the impact parameter becomes larger,which indicates a smaller source.Also,the two-and three-pion correlation functions become low when the pions from resonance decay are includ-ed.The study of normalized three-pion correlation factor indicates that the pion-emitting sources in the Au-Au collisions,simulated by AMPT model at (?)=200 GeV at the RHIC,are highly incoherent.