Strangeness production in a quark-gluon plasma
This thesis is arranged as follows: Chapter 1 notes that the production of strangeness measured at CERN and Brookhaven has two possible explanations. One is that strange quarks, being relatively light, are easily produced, creating an abundance of strange particles in the experiment. On the other hand, hadron gas models use only thermodynamics, strangeness neutrality and baryon number conservation to predict the same ratios. Both models need a parameter, ϒs, reflecting the relative departure from equilibrium of strangeness. Chapter 2 discusses the Cutkosky rules and their thermal field theory counterparts, the Kobes-Semenoff rules. The influence of the medium is brought into consideration through Braaten-Pisarski resummation. In Chapter 3 we use the Cutkosky rules to calculate the standard QCD quark production mechanisms. The intention is to eventually generalise these calculations to finite temperature. We then derive the rate of plasmon decay (gluons pick up finite masses and widths due to interactions with the medium), which was proposed by Tanguy Altherr and David Seibert to be another important mechanism for the production of strangeness. In Chapter 4 we use Bjorken's framework of one-dimensional hydrodynamic flow to study the evolution of a gluon plasma, through the production of quarks to a later stage, by which times hadrons should be prevalent. Of critical importance is the thermal equilibration time. We derive some analytic expressions for the proper time dependence of the chemical potential and temperature of the quark-gluon plasma. Chapter 5 concludes this thesis and sets out a program to be continued. The Appendices summarise some useful data, notation and concepts with regard to make reading easier and to be used in continuing this research. Specifically the propagators and vertices of Thermal Field Theory (TFT) are listed as well as the cut propagators. Finally, at the end are listed acknowledgments and a bibliography.
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