A Parton-Hadron Cascade Approach in High-energy Nuclear Collisions

Event generators based on perturbative QCD (pQCD) are proposed such as HIJING (Heavy Ion Jet Interaction Generator)[1], VNI (Vincent Le Cucurullo Con Giginello)[2], in order to describe ultra-relativistic heavy ion collisions, especially, at collider energies (RHIC/LHC). Although both models reproduce many pp and p̄p data, there are large discrepancies in AA collisions between these two models, for example, absolute number of produced particles, slope of transverse momentum. The main differences of the modeling between these two models are following: VNI is a Monte Carlo implementation of parton cascade model (PCM) in which the time evolution of heavy ion collision is simulated by the parton cascading. While HIJING assumes the Glauber theory in the description of AA collisions and handles the soft process based on the string model. Namely, the treatment of the multiple parton and hadron interactions is different. Second, the cut-off p0 has to be introduced to avoid divergent QCD cross section for p⊥ → 0 and this value is model dependent. In order to understand particle production mechanism in nuclear collisions, the role of multiple interactions as well as the sensitivity of model parameters should be carefully investigated. Hadronic microscopic transport models such as RQMD [3] ARC [4], QGSM [5] and UrQMD [6] have been successfully applied to nuclear reactions at AGS and SPS energies. Thus, the purpose of this work is to include hard processes into hadronic transport model by using HIJING formalism and study the effect of multi-step interaction on particle spectra at collider energies.