  For central PbPb collisions at a center of mass energy of 17.3 GeV/nucleon we
have made the first two-dimensional measurement of the pp correlation function.
These data extend the range of previous studies of HBT radii by a factor of two
in transverse mass. They are consistent with a hydrodynamic interpretation and
microscopic models that include hadronic rescattering and transverse expansion.
We also report new data on pion correlations. The two particle correlations of
negative pions at a transverse mass of 0.92 GeV imply source radii that are
smaller than typical hydrodynamic fits and transport model simulations. It is
possible that these fast pions may have left the source before the build up of
hydrodynamic flow.
