We analyze the recent data from the BRAHMS Collaboration on the pseudorapidity dependence of nuclear modification factors in $\text{Au}+\text{Au}$ collisions at $\sqrt{s_{NN}}=200\text{GeV}$ by using the full three dimensional hydrodynamic simulations for the density effects on parton energy loss. We first compute the transverse spectra at $\eta =0$ and 2.2, and next take a ratio $R_{\eta }=R_{AA}(\eta =2.2)∕R_{AA}(\eta =0)$, where $R_{AA}$ is a nuclear modification factor. It is shown that hydrodynamic components account for $R_{\eta }\simeq 1$ at low $p_{\mathrm{T}}$ and that quenched perturbative QCD components lead to $R_{\eta }<1$ at high $p_{\mathrm{T}}$ which are consistent with the data. Strong suppression at $\eta =2.2$ is compatible with the parton energy loss in the final state.

• Received 28 July 2003

DOI:https://doi.org/10.1103/PhysRevC.68.064902