A perturbative QCD analysis of charged-particle distributions in hadronic and nuclear collisions

We compute the distributions of charged particles at large transverse momenta in p (p) over bar (p), pA and AA collisions in the framework of perturbative QCD, by using collinear factorization and the modem PDFs and fragmentation functions. At the highest cms-energies the shape of the spectra measured in p (p) over bar (p) collisions at large q(T) can be well explained. The difference between the data and the lowest-order computation is quantified in terms of a constant K-factor for each energy. The K-factor is found to systematically decrease with growing roots. Also a lower limit for the partonic transverse momentum, p(0), is extracted for each roots based on the comparison with the measurements. A systematic increase of p(0) as a function of roots is found. Nuclear effects in the charged-particle spectra in pA and AA collisions at RHIC and LHC are studied in the framework of collinear factorization by applying the EKS98 nuclear corrections to the parton distributions. The nuclear effects are shown to mostly enhance the computed spectra. A comparison with the recent PHENIX data from central and peripheral An + Au collisions at RHIC is done. (C) 2002 Elsevier Science B.V. All rights reserved.