CHARM and Strangeness in Quark-Gluon Plasma Hadronization

Abstract

This dissertation presents a theoretical study of soft hadron production in relativistic heavy-ion collisions. The aim is to explore the principles governing the hadronization of the expanding quark-gluon plasma (QGP) fireball, and to understand its properties. Strange hadron production and strangeness abundance in the QGP help us to look before the instant of hadronization. Consideration of entropy and charm production further enhances the reach back in time to the first instances of the heavy ion collision. Much of the ongoing effort is to demonstrate the validity of a QGP hadronization model which describes the particle production data accurately and thus allows us to carry out the above research program. We perform a centrality dependent study of multistrange hadrons from Au-Au collisions at √SNN = 62.4 GeV, data obtained at the Relativistic Heavy Ion Collider (RHIC). We show that the statistical hadronization model (SHM) well describes particle production. For all centralities, the particle production conditions are compatible with the earlier proposed critical hadronization pressure suggesting a set of universal hadronization conditions of QGP. Heavy-ion collisions at the Large Hadron Collider (LHC) present a new challenge for SHM in describing particle production at TeV energy scales. The chemical non-equilibrium model gives a good description of the hadron production in Pb-Pb collisions at √SNN = 2.76 TeV consistently as a function of centrality. Moreover, the model parameters, such as chemical freeze-out temperature, assume expected values suggested by results from previous studies at lower energies. The quark-gluon plasma fireball hadronizes at the same universal hadronization conditions, that is a common critical pressure, entropy and energy density. At LHC energies, a significant amount of charm is expected to be produced. It is therefore crucial to incorporate charm into the present description of particle production. We present a new tool, an upgraded SHARE with CHARM program, that quantifies the effect of charm on the yield of lighter hadrons and physical properties of the hadronizing fireball. In addition to light flavors (u,d,s), SHARE with CHARM describes charm hadron production and decays of charm hadrons. According to present experimental results, charm decays mainly affect the yields of multistrange particles. This dissertation begins with an introduction to the particle production in heavy-ion collisions and SHM framework, followed by a summary of results that are either published or submitted to peer-reviewed journals and others which are published as conference proceedings. Reprints of the publications are attached to the dissertation as appendices. Each appendix is prefaced with a short summary of presented results, and my contribution to these works is described.