The Coalescence Rates For Hadron Production In Relativistic Heavy Ion Collisions

Quantum Chromo-dynamics predicts a new form of matter named Quark-Gluon Plasma may be produced by extremely high temperature or high energy densities.In the big bang theory,the QGP exists within a millionth of a second after the big bang in the universe.The study of QGP is one of the most important ways to understand the origin of the universe and verify the standard model. Currently,the only way we can controll to study QGP in the laboratory is by the relativistic heavy ion collisions. The RHIC in Brookhaven National Laboratory and the LHC at CERN are committed to the study of QGP,and as we know, some signatures for QGP formation have been found in RHIC and LHC. LHC collision energy is also being risen for a more comprehensive understanding of QGP.We can simply divide the process of relativistic heavy ion collisions into two stages:the evolution of the initial stage and the stage of hadronization. Nowadays, the only way to explore the generation mechanism of the process of hadronization is through the establishment of various models for final state particle production. In this paper, we describe a very successful model of the process for hadronization :quark recombination model by the Oregon Group(Hwa/Yang model).This model first introduced the concept of shower partons,assuming all gluons being converted into the quark anti-quark pair before the process of hadronization. The partons arc assumed in local thermal equilibrium, and all final state hadrons are produced by the combination of the thermal partons and shower partons. Then we introduce the theory and basic formulas of ALCOR modelIn this thesis we use a potential model with Lorentz vector short-range poten-tial and the Lorentz vector confinement potential for the light quark system,with the correction of quark condensate and gluon condensate included.Then we calculate the coalescence rate for meson production in the ALCOR model. First, we determine the quark coalescence amplitude in rearrangement reaction from quantum mechanics. Then we consider the the influence of damping factor and the width of Gaussian wave functions in the quark coalescence amplitude, and calculate the meson production rate.Our calculations show that:the type of pre-meson wave function has little effect on the reaction rate. Through analysis, we believe that the temperature dependence of reaction rate is small, proving the applicability of coalescence model for cross-over phase transition. Reaction rate depends on the damping factor for the quark inter-action potentialμ.The greater the damping factor, the slower reaction rate.Rcaction rate depends on the width of Gaussian wave functions.