Probing the Long Range Nature of Pion Emission Source at SPS Energies

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 function is essentially Gaussian from 20 AGeV to 80 AGeV but it displays significant non‐Gaussian tails at 158 AGeV.