We present the first excitation function of ${\pi }^{-}$ intensity interferometry at Alternating Gradient Synchrotron (AGS) energies (2–8 A GeV). The sensitivity of the multidimensional correlation functions to the geometry and dynamics of the pion-emitting system provides a stringent test of transport models of heavy ion collisions. Detailed comparisons with a realistic transport model, both with and without an explicit nuclear mean field, suggest that the beam energy evolution in the reaction dynamics is different in the model than in the data. A significantly increased ${\pi }^{-}$ emission time scale, which has been suggested as a signal of the onset of the transition to quark-gluon plasma, is not observed.

• Received 6 December 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.2798