Back-to-Back Correlations Of Boson-Antiboson Pairs In High Energy Heavy Ion Collisions

In the hot and dense hadronic sources created in high energy heavy ion collisions, the particle mass-shift due to medium interactions might lead to a squeezed correlation of boson-antiboson pairs, as so called back-to-back correlation (BBC).In this dissertation, we develop a technique of relativistic calculation for the BBC of boson-antiboson pairs by Monte Carlo simulation. The relativistic effects on the BBC func-tions of ??) and K+K-pairs are investigated. The investigations indicate that the relativistic effect on the BBC functions of K+K-which have smaller mass is significant, and the rela-tivistic effects are sensitive to the particle freeze-out temperature.Motivated by the anisotropy of particle-emitting sources formed in high energy heavy ion collisions, we study the BBC functions of ??> and K+K-for anisotropic hadronic sources. It is found that the BBC functions depend not only on the magnitude of particle momentum, but also on its direction. As the source expanding velocity increases, the BBC function increases when the particle momentum is approximately perpendicular to the source velocity, and the BBC function decreases when the particle momentum is approximately parallel to the source velocity.Relativistic hydrodynamics has been extensively applied to high energy heavy ion col-lisions. It has successfully explained a lot of experimental phenomenons. We investigate the BBC functions of ?? and K+K- for hydrodynamic sources. The results indicate that the BBC functions exhibit oscillations as a function of the particle momentum for the hy-drodynamic sources with Gaussian initial energy distributions. The BBC functions decrease with increasing absolute value of the particle pseudo-rapidity. For the transverse anisotropic sources, the BBC functions are minimum when the azimuthal angles of the particles reach zero.Recent investigations indicate that the local equilibrium systems created in high ener-gy heavy ion collisions are fluctuated and inhomogeneous. In this dissertation, we use the HIJING generator in AMPT model to simulate the fluctuating initial conditions in the col-lisions of Au+Au at (?) 200 GeV at the RHIC and Pb+Pb at (?)=2.76 TeV at the LHC, and investigate the BBC of boson-antiboson for the hydrodynamic sources with the fluctuating initial conditions. The results indicate that the BBC functions averaged over event-by-event calculations are smoothed as a function of the particle momentum for the hydrodynamic sources with the fluctuating initial conditions. The BBC functions of ?? are greater than those of K+K-. They increase with increasing collision centrality and decrease with increasing collision energy, and exhibit an obvious dependence on pseudo-rapidity. As the BBC is very sensitive to the temporal distribution of source freeze-out points, we further calculate the BBC function of ?? for the hydrodynamic sources for the collisions of Cu+Cu at (?) 200 and 62.4 GeV at the RHIC. The BBC function of ?? for the collisions of Cu+Cu at (?)62.4 GeV is greater because of the shorter lifetime of the small collision system.