Rapidity dependence of Bose-Einstein correlations at SPS energies
  This article is devoted to results on pion-pion -Bose-Einstein correlations in central Pb+Pb collisions measured by the NA49 experiment at the CERN SPS. Rapidity as well as transverse momentum dependences of the correlation lengths will be shown for collisions at 20A, 30A, 40A, 80A, and 158A GeV beam energy. Only a weak energy dependence of the radii is observed at SPS energies. The kt-dependence of the correlation lengths as well as the single particle mt-spectra will be compared to model calculations. The rapidity dependence is analysed in a range of 2.5 units of rapidity starting at the center of mass rapidity at each beam energy. The correlation lengths measured in the longitudinally comoving system show only a weak dependence on rapidity. 
Stefan Kniege (for the NA49 Collaboration)