High Energy Nuclear Reactions and Creation of Quark-Gluon Plasma

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The purpose of this research was to investigate the mechanism of multi-particle production of hadrons in high-energy collisions involving nuclei, and the dynamics of quark-gluon plasma.For this purpose, we adopted two approaches. The first is to investigate dynamical aspects of quark-gluon plasma on the basis of hydrodynamical equation. The second is to develop event generation program for multi-chain model as a standard model of nucleus collisions, so as to confront the forthcoming data of high energy nucleus-nucleus collision.In the first approach, assuming the emergence of the quark-gluon plasma, we have analyzed its time-development on the basis of three-dimensional relativistic hydrodynamical equation of motion. As a result of numerical calculation, we found that transverse motion of the fluid have strong influence on the transverse momentum of produced hadrons and that its distribution gives an information of the initial state of the quark-gluon plasma.In the second approach, we have studied jets in electronpositron pair annihilation using quark cascade model and analyzed heavy quark fragmentation in detail. Moreover, we constructed hadronic chain model for the analysis of high-energy collision of hadrons and/or nuclei and developed an event generation program using Monte-Carlo method. This is necessary to distinguish new phenomena such as production of quark-gluon plasma from the backgrounds. We found that this model describes dominant features in hadron-hadron collision and is also useful for the high-energy collisions involving nuclei.