Extracting particle freeze-out phase-space densities and entropies from sources imaged in heavy-ion reactions - art. no. 014904

The space-averaged phase-space density and entropy per particle are both fu ndamental observables which can be extracted from the two-particle correlat ion functions measured in heavy-ion collisions. Two techniques have been pr oposed to extract the densities from correlation data: either by using the radius parameters from Gaussian fits to meson correlations or by using sour ce imaging, which may be applied to any like-pair correlation. We show that the imaging and Gaussian fits give the same result in the case of meson in terferometry. We discuss the concept of an equivalent instantaneous source on which both techniques rely. We also discuss the phase-space occupancy an d entropy per particle. Finally, we propose an improved formula for the pha se-space occupancy that has a more controlled dependence on the uncertainty of the experimentally measured source functions.