Hadron production in heavy ion collisions: Fragmentation and recombination from a dense parton phase
We discuss hadron production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). We argue that hadrons at transverse momenta P T<5 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 PT>2 GeV. Below PT=2 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 v2 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 MeV and a radial flow velocity of 0.55c.