th / 0 30 60 19 v 1 4 J un 2 00 3 Pion production in d + Au collisions at RHIC energy

Neutral pion (π 0) production is calculated in a next-to-leading order (NLO) perturbative QCD-based model in pp and dAu collisions at √ s = 200 AGeV. The model includes the transverse component of the initial parton distribution (" intrinsic k T "). We compare the results of our NLO calculations for pp collision to the available experimental data from RHIC, and fit the data with high precision. The calculation tuned this way is repeated for the dAu collision, and, after including proper multiscattering and shadowing effects, we make predictions for the forthcoming RHIC experiments. The centrality dependence of the nuclear modification factor shows a measurable difference between shadowing parameterizations. Recent experimental data on mid-rapidity π 0 production in the transverse momentum region 2 GeV < p T < 10 GeV measured at the Relativistic Heavy Ion Collider (RHIC) in Au + Au collisions at √ s = 130 AGeV and 200 AGeV display surprising evidence of new phenomena appearing in hot dense matter. Here we focus on the property that the π 0 transverse momentum spectrum shows a strong suppression[1, 2] in central collisions compared to theoretical expectations based on binary collision dynamics in perturbative quantum chromodynamics (pQCD) calculations (see e.g. Ref.s [3, 4, 5]). A similar suppression pattern was observed for charged hadrons [6]. Introducing final state interactions, The entanglement of initial and final state interactions in Au + Au collisions and the complexity of the appropriate theoretical calculation generated an increased interest in simpler heavy-ion induced reactions, such as the d + Au collision. In this case final state interactions play a minor role, and the initial state interactions (initial multiscattering, shadowing) can be investigated cleanly. The