  The scaling of pion multiplicities with system size in proton-nucleus and
nucleus-nucleus reactions at 200 A GeV is investigated. A nuclear geometry
calculation of incoherent multiple scattering including effects of deceleration
of the participating particles is presented. Pion multiplicities at high
transverse momenta agree relatively well with an overall scaling with the
number of binary collisions. The deviations from this gross scaling for p+A and
S+Au reactions at 200AGeV are compared to model predictions and the
implications are discussed. Within this picture no universal scaling law for
high pT particle production is obtained. In addition to the conceptual problems
of such an incoherent model, it is shown that the implied kinematic relation
between a possible pT-broadening and deceleration leads to contradictions. The
scaling of pion production at intermediate pT with system size does not
indicate a multiple scattering enhancement.
