Towards Reconstructing the Final Stage of Heavy Ion Collisions

A Fourier inversion problem lies at the heart of determining spatio-temporal characteristica of the final stage of a heavy ion collision: From the measured two-particle momentum correlations C(p_1,p_2) of identical particles, pions say, a Hanbury-Brown /Twiss (HBT) interferometric analysis aims at extracting as much information as possible about the Wigner phase space density S(x,p) of pion emitting sources in the collision region. Here, we discuss how this analysis allows to separate the effects of temperature and transverse flow which cannot be disentangled completely on the basis of single-particle spectra.