Nucleon shadowing effects in Cu + Cu and Au + Au collisions at RHIC within the HIJING code

Abstract

The centrality dependence of pseudorapidity density of charged particles (dNch/dη) in Cu + Cu (Au + Au) collisions at Relativistic Heavy Ion Collider energy of √sNN = 22.4, 62.4 and 200 (19.6, 62.4 and 200) GeV, is investigated within an improved HIJING code. The standard HIJING model is enhanced by a prescription for collective nucleon-nucleon (NN) interactions and more modern parton distribution functions. The collective NN-interactions are used to induce both cascade and nucleon shadowing effects. We find collective cascade broadens the pseudorapidity distributions in the tails (at|η| > ybeam) above 25%-30% collision centrality to be consistent with the dNch/dη data at √SNN = 19.6, 22.4, 62.4 GeV. The overall contribution of nucleon shadowing is shown to depress the whole shape of dNch/dη in the primary interaction region (at |η| > ybeam) for semiperipheral (20%-25%) and peripheral (≥35%-40%) Cu + Cu (Au + Au) interactions at √SNN = 200 GeV, in accordance with the PHOBOS data.