BEC, the τ-model, and jets at the Z pole

Bose-Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various parametrizations. A good description is achieved using a Levy stable distribution in conjunction with a model where a particle's momentum is highly correlated with its space-time point of production, the τ-model. However, a small but significant elongation of the particle emission region is observed in the Longitudinal Center of Mass frame, which is not accommodated in the τ-model. Further, for three-jet events the region is found to be larger in the event plane than out of the plane. (author)