The centrality dependence of the source size for AuAu collisions at the AGS

Recent π − π − correlation measurements and deuteron to proton yield ratio measurements for AuAu collisions from Brookhaven E866 are presented. These measurements allow us, with some interpretation, to deduce the size of the participant region in a heavy ion collision. An unpredicted rise of the apparent source size is seen in the π − π − data at midrapidity. No corresponding drop in the deuteron to proton yield ratio is seen. Further experimental study is needed to improve the statistical significance of the correlation result and to determine whether it can be explained by conventional hadronic means.