Scaling of particle production with number of participants in high-energy A plus A collisions in the parton-cascade model

In view of the recent WA98 data of pi(0) spectra from central Pb + Pb colli sions at the CERN SPS, we analyze the production of neutral pions for A + A collisions across the periodic table at root s = 17 AGeV and 200 AGeV with in the framework of the parton-cascade model for relativistic heavy ion col lisions. The multiplicity of the pions (having p(T) > 0.5 GeV) in the centr al rapidity region, is seen to scale as similar to (N-part)(alpha), where N -part is the number of participating nucleons, which we have approximated a s 2A for central collisions of identical nuclei. We argue that the deviatio n of alpha (similar or equal to 1.2) from unity may have its origin in the multiple scattering suffered by the partons. We also find that the constant of proportionality in the above scaling relation increases substantially i n going from SPS to RHIC' energies. This would imply that the (semi)hard pa rtonic activity becomes a much cleaner signal above the soft particle produ ction at the higher energy of RHIC, and thus much less dependent on the (la ck of) understanding of the underlying soft physics background.