Statistical hadronization phenomenology in heavy ion collisions at SPS and RHIC energies

Abstract

This dissertation examines the phenomenology of statistical hadronization at ultrarelativistic energies. We start with an overview of current experimental and theoretical issues in Relativistic heavy ion physics. We then introduce statistical hadronization, and show how it gives a description of particle abundances and spectra through covariance and entropy maximization. We argue that a distinction can be made between equilibrated staged freeze-out in which post-formation hadron interactions play an important role in determining final-state observables, and non-equilibrium sudden freeze-out where spectra and abundances get determined at the same time and further interactions are negligible. We attempt to falsify sudden freeze-out by examining whether particle abundances and spectra can be described using the same formation temperature. This is done both in the equilibrium framework, and using a chemical non-equilibrium ansatz. Our fits to experimental data suggest that the sudden freeze-out model explains both the particle abundances and spectra. We then try to extract the particle formation temperature, and quantify post-freeze-out hadronic interactions using experimentally observable resonances. We discuss observed resonances and suggest further measurements that have the potential to distinguish between the possible freeze-out scenarios experimentally. Finally, we infer from experimental data how particle formation proceeds in spacetime, in particular whether freeze-out dynamics agrees with the sudden freeze-out expectation. We examine particle spectra, and show that they are not sensitive enough to pick the right freeze-out dynamics. We suggest resonances and azimuthal anisotropy as experimental probes for this task.