Multidimensional HBT correlations in proton-antiproton collisions at   root(s) = 630 GeV
  We analyse second moments $R_2$ of like-sign pion pairs in the two-dimensional $(q_L,q_T)$ and three-dimensional $(q_O,q_S,q_L)$ decompositions of the three-momentum difference. Conventional fit parametrisations such as gaussian, exponential, power-law and Edgeworth fail miserably, while more elaborate ones such as Levy do well but fail to yield a unique best-fit solution. A two-component model using a hard cut to separate small- and large-scale parts appears possible but not compelling. In all cases, the data exhibits a strong and hitherto unexplained peak at small momentum differences which exceeds current fits. 
H. C. Eggers, B. Buschbeck and F. J. October