The Effect Of Bose-Einstein Condension On The Chaoticity Parameter In Three-Pion Interferometry

The HBT(Hanbury-Brown-Twiss) intensity interferometry is an important and effective kind of tool in the field of high energy heavy-ion collisions, using the HBT intensity interferometry can gain much information about the space-time structure of the source. The chaoticity parameters is an artificially introduced phenomenological parameter used to describe the degree of chaos of the source, the higher degree of chaos the source has, the larger value the chaoticity parameters has.In nowadays the energy of heavy ion collisions increases larger and larger, especially within the scope of LHC or RHIC energy ranges, in a collision event, the identical pion multiplicity can reach to hundreds and even thousands, a great deal of particles assemble in a small space, There is a great possibility for these particles which are in the Bose Einstein condensation, however, the HBT intensity interferometry won’t exist when the source is a completely coherent source, some existing studies had proved that the Bose Einstein condensation can impact on the chaoticity parameter λ2 in two-pion interferometry, and in resent experiments at LHC, by using the three-pion correlation function to analysis date, people find that the sources isn’t completely chaos. Basing on these studies, in this thesis it studies the Bose-Einstein condensation impacts on the chaoticity parameter λ3 of three-pion interferometry which occurs in the Gaussian expending pion sources.In this thesis, it states the developments of the HBT intensity interferometry briefly, according to the intensity interferometry and quantum statistic fundamental theory, derive the partially coherent sources’ three-pion correlation function C3 for with the base of two-pion correlation function C2, basing on the genuine three-pion correlation functions c3 to construct the relative three-pion correlation function r3 and using the intercept of r3 to calculate the chaoticity parameter of three-pion interferometry in the Gaussian expending pion sources with different degree of chaos. The result of this study shows that when there are many particles in the sources, there will have the Bose Einstein condensation phenomenon, then the chaoticity parameter λ3 of three-pion interferometry have a strong correlation with the Bose Einstein condensation, while the Bose Einstein condensation effect decrease just a little, the value of the chaoticity parameter λ3 will have obvious increasing.