Energy and System-size Dependence of Two-particle Azimuthal Correlations   of High-pT Charged Hadrons at the CERN SPS
  Angular correlations of high-pT hadrons can serve as a probe of interactions of partons with the dense medium produced in high-energy heavy-ion collisions but other sources of such correlations exist which can be non-negligible SPS energies. In an attempt to determine the primary source, NA49 has performed an energy and system-size scan of two-particle azimuthal correlations in central Pb+Pb, Si+Si and p+p collisions at 158A GeV, as well as central Pb+Pb collisions at 20A, 30A, 40A and 80A GeV. Moreover, results at 158A GeV have been compared to UrQMD simulations. 
Marek Szuba (for the NA49 Collaboration)