Transverse-longitudinal HBT correlations in pp¯ collisions at s=630 GeV

Correlations of like-sign pion pairs emerging from proton-antiproton collisions are analysed in the two-dimensional (qL,qT) decomposition of the three-momentum difference q. While the data cannot be adequately represented by Gaussian, exponential, power-law or Edgeworth parametrisations, more elaborate ones such as Lévy and an exponential with a cross term do better. A two-scale model using a hard cut to separate small and large scales may indicate a core that is more prolate than the halo. Consideration not only of the interference peak at small (qL,qT), but also of the shape of the correlation distribution at intermediate momentum differences is crucial to understanding the data.