Particle production in high-energy nuclear collisions: Parton cascade—cluster hadronization model

Abstract

A phenomenological cluster hadronization scheme for partons in nuclear collisions is presented and combined with the earlier developed parton cascade model to provide a comprehensive description of highly relativistic hadron-hadron and nucleus-nucleus collisions. The model as a whole allows one to study the time evolution of the collisions in complete phase space from the instant of nuclear contact, via the perturbative QCD evolution of parton distributions, to the formation of final hadronic states. The application of this approach to $p\overline{p}$ collisions at $\sqrt{s}=200\ensuremath{-}1800$ GeV yields a decent agreement with the experimentally measured momentum and multiplicity distributions. Heavy ion collisions are illustratively studied in the case of central Au + Au collisions at energies of the BNL Relativistic Heavy Ion Collider (RHIC) ($\sqrt{s}=200A$ GeV) and the CERN Large Hadron Collider (LHC) ($\sqrt{s}=6300A$ GeV). The impact of a number of nuclear and medium effects on the inclusive hadron production is analyzed and predictions for charged particle spectra and multiplicities are given. In particular, the model results for the central rapidity densities of charged particles are $\ensuremath{\simeq}1200(\sqrt{s}=200A \mathrm{GeV})$ and $\ensuremath{\simeq}2500(\sqrt{s}=6300A\mathrm{GeV})$, which is a factor of \ensuremath{\sim} 2.5 per nucleon larger than in $p+p$ collisions at corresponding energies.