Hadron production in central nucleus-nucleus collisions at chemical freeze-out

We discuss hadron production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) We argue that hadrons at transverse momenta ${P}_{T}l5\phantom{\rule{03em}{0ex}}\text{GeV}$ are formed by recombination of partons from the dense parton phase created in central collisions at RHIC We provide a theoretical description of the recombination process for ${P}_{T}g2\phantom{\rule{03em}{0ex}}\text{GeV}$ Below ${P}_{T}=2\phantom{\rule{03em}{0ex}}\text{GeV}$ our results smoothly match a purely statistical description At high transverse momentum hadron production is well described in the language of perturbative QCD by the fragmentation of partons We give numerical results for a variety of hadron spectra, ratios, and nuclear suppression factors We also discuss the anisotropic flow ${v}_{2}$ and give results based on a flow in the parton phase Our results are consistent with the existence of a parton phase at RHIC hadronizing at a temperature of $175\phantom{\rule{03em}{0ex}}\text{MeV}$ and a radial flow velocity of $055c$

Hadron production in heavy ion collisions: Fragmentation and recombination from a dense parton phase

Chemical freeze-out and the QCD phase transition temperature

We analyze the centrality dependence of thermal parameters deduced from hadron multiplicities in Au+Au collisions at $\sqrt{{s}_{\mathrm{NN}}}=130 \mathrm{GeV}$ Although the chemical freeze-out temperature and chemical potentials are found to be roughly centrality independent, the strangeness saturation factor ${\ensuremath{\gamma}}_{S}$ increases with participant number toward unity, supporting the assumption of equilibrium freeze-out conditions in central collisions

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J. Schaffner-Bielich

Papers

Particle ratios at RHIC: Effective hadron masses and chemical freeze-out