Directional dependence of the pion source in high-energy heavy-ion collisions

π+π+ and π−π− correlations from 200 GeV per nucleon S + Pb collisions and π+π+ correlations from 450 GeV p + Pb collisions measured by the focussing spectrometer of CERN experiment NA44 are presented. The large data set which emphasizes small values of momentum difference allows multi-dimensional analysis along with the more traditional one-dimensional parameterization to characterize the pion emission source. It is found that the three radius parameters are similar and large compared to the projectile radius. This can be explained by pion scattering in the final state hadronic system.