Evidence for non-gaussian tail in 3-dimensional pion emission source at SPS

Abstract

The NA49 experiment at CERN SPS has acquired a huge data set of Pb+Pb events over a broad range of energy and centrality during the last several years. This high statistics data set, coupled with a state-of-the-art analysis technique, allows for the first model-independent extraction and energy scan of 3D emission sources for pion pairs at SPS energies. These 3D pion emission sources provide new insights into the nature of a long-range source previously reported by PHENIX at RHIC. The new results indicate that the pion source displays significant non-Gaussian tails in the longitudinal direction at 40 and 158 AGeV and in the outward direction at 158 AGeV.PACS numbers: 25.75.Gz, 25.70.Pq