Theoretical Study Of Heavy Quarkonia As A Probe Of Quark Matter

Quarks and gluons are usually confined in nucleons. However, in a state with high temperature or pressure, the partons may behave like free particles and reach asymptotic freedom, they may form a new state of matter, called QGP(Quark-Gluon-Plasma). Light hadrons with small binding energy can easily be dissolved due to the color screening in the QGP. Heavy quarkonia with much larger binding energy may survive in this hot medium, and can be a good probe to study the properties of QGP. Also, the study on heavy quarkonia can tell us a lot about strong interactions in hot and dense medium.In this thesis, a Boltzmann-type transport equation is used to describe the dissociation and regeneration of heavy quarkonia in QGP. The properties of heavy quarkonia in hot medium are so di?erent from that in vacuum due to the color screening e?ect.We use the mean field method to simulate this e?ect, and solve the Boltzmann equation self-consistently. We find that the initial charmonium production is not sensitive to this e?ect, but the yield of regenerated charmonia is largely enhanced. The excited states of charmonia can barely survive in QGP due to their low dissociation temperature. We find that most of the charmonium excited states comes from B hadron decay. At lower colliding energies, the contribution from hadron gas should not be neglected, especially in peripheral collisions where the produced matter may exist in hadron phase. In central collisions, the suppression from QGP is necessary for the experimental data of heavy quarkonia. From the connection between properties of QGP and production of heavy quarkonia, we find that the quarkonium production is not sensitive to both shear viscosity and fluctuations of initial energy density of QGP, but to the formation time of the hot medium. This makes heavy quarkonia a good probe to the early formation of QGP.