How to Test the Existence of the Early Parton Cascade using Photon HBT Correlations

We report on a possible application of the HBT phenomenon in testing the existence of two hypothetical phenomena. First, it is argued that the existence of a rapidly developing parton cascade in the earliest stages of a high energy nuclear collision process can be tested by studying two-photon HBT correlations over a <I>wide</I> longitudinal momentum scale - corresponding to the <I>early</I> photon emission time from the hypothetical parton system. This method provides the selectivity for the early emitted photons, since the photons emitted at later times correlate over progressively narrower momentum scales. Second, in a similar way we argue that the existence of a hypothetic dark matter candidate, the Weakly Interacting Massive Particle (WIMP), may be tested by studying HBT correlations of cosmic gamma rays at a relatively <I>long</I> detection time scale - corresponding to the very <I>narrow</I> spectral line of the photons emerging from WIMP annihilations. Background photons leave no signature since they do not correlate.