Obtaining The Chaoticity Parameter Of Partially Coherent Source With Three-pion Interferometry

In high energy heavy ion collisions, pions are the most produced particles. Pion interferometry has become the important tool to study the space-time structure and coherent degree of the particle emission sources in high energy heavy ion collisions. As the energy of heavy ion collisions increases, the number of the identical pions produced in a collision event becomes larger and larger. The conditions are ripe for a careful investigation to the multi-pion correlations.In this thesis, we first give a brief review and statement on the developments and states of intensity interferometry. The theory formulism and simulation calculations of the two-pion interferometry for partially coherent sources are introduced. Then, we present the derivations of the three-pion correlation function 3C and the pure three-pion correlation functions 3c for the partially coherent sources. We analyze the three-pion and pure three-pion correlation functions for the partially coherent sources with Gaussian density distributions by simulation calculations. On these bases, we construct the relative three-pion correlation function 3r, and extract the chaoticity parameters of the partially coherent sources through analyzing the intercepts of 3r at the approximate zero relative momentum. The experimental results of the chaoticity parameter in three-pion interferometry for the collisions of 2.76 NNs = Te V Pb+Pb at CERN-LHC are discussed. The investigations in the thesis indicate that the three-pion correlation functions are more sensitive to the coherence degree of the partially coherent sources, as compared to the two-pion correlation functions. One can obtain the chaoticity parameter of the particle-emitting sources produced in high energy heavy ion collisions, by measuring the values of 3r at the approximate zero relative momentum.