(Anti)Proton and Pion Source Sizes and Phase Space Densities in Heavy Ion Collisions

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NA44 has measured mid-rapidity deuteron spectra from AA collisions at sqrts=18GeV/A at the CERN SPS. Combining these spectra with published proton, antiproton and antideuteron data allows us to calculate, within a coalescence framework, proton and antiproton source sizes and phase space densities. These results are compared to pion source sizes and densities, pA results and to lower energy (AGS) data. The antiproton source is larger than the proton source at sqrts=18GeV/A. The phase space densities of pions and protons are not constant but grow with system size. Both pi+ and proton radii decrease with transverse mass and increase with sqrts. Pions and protons do not freeze-out independently. The nature of their interaction changes as sqrts, and the pion/proton ratio increases.