Hanbury Brown-Ttiss Correlation Functions from Event Generators: A   Reliable Approach to Determine the Size of the Emitting Source in   Ultrarelativistic Heavy Ion Collisions?
  Employing NEXUS, one of the most recent simulation programs for heavy ions collisions, we investigate in detail the Hanbury-Twiss correlation function for charged pions for reactions 158 GeV Pb+Pb. For this study we supplement the standard simulation program by electromagnetic interactions. We find that the string fragmentation introduces strong space-momentum correlations and the freeze out times of the correlated pairs have a wide distribution. Both has a strong influence on the apparent source radius determined from the measured correlation correlation function.An equally strong influence is observed for the final state electromagnetic interaction. 
F. Gastineau, J. Aichelin