Three-Dimensional Two-Pion Emission Source at SPS: Extraction of Source   Breakup Time and Emission Duration
  A model-independent, three-dimensional source function for pion pairs has been extracted from Pb+Pb collisions at $\sqrt s_{NN}=17.3$ AGeV. The extracted sourc e exhibits long-range non-Gaussian tails in the directions of the pion-pair net transverse-momentum and of the beam. Comparison with the Therminator model allow s for an extraction of the pion source proper breakup time and of emission durat ion in the collisions. 
P. Chung and P. Danielewicz