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

The centrality dependence of pseudorapidity density of charged particles (${dN}_{ch}/d\eta$) in Cu + Cu (Au + Au) collisions at Relativistic Heavy Ion Collider energy of $\sqrt{s_{{}_{NN}}}=22.4$, 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 $|\eta |>y_{beam}$) above 25%–30% collision centrality to be consistent with the ${dN}_{ch}/d\eta$ data at $\sqrt{s_{{}_{NN}}}=19.6,22.4,62.4GeV$. The overall contribution of nucleon shadowing is shown to depress the whole shape of ${dN}_{ch}/d\eta$ in the primary interaction region (at $|\eta |<y_{beam}$) for semiperipheral (20%–25%) and peripheral ($⩾35\%\text{--}40\%$) Cu + Cu (Au + Au) interactions at $\sqrt{s_{{}_{NN}}}=200GeV$, in accordance with the PHOBOS data. (paper)