Modification of jet-like correlations in Pb-Au at the SPS

Abstract

A study of high- p t two-particle azimuthal correlations in Pb-Au at S NN = 17 , 2 GeV by the CERES experiment at the CERN-SPS, is presented. A broad away-side correlation with significant dip at Δ ϕ ≈ π is observed. The shape and magnitude of the correlation is similar to measurements at RHIC. In comparison to PYTHIA calculations, we observe a significant excess of soft particles at the away-side. A study of charge correlations between trigger and associated particles disfavors vacuum fragmentation of the away-side jet and suggests significant energy transfer of the hard-scattered parton to the medium.