Rapidity-alignment and pT compensation of particle pairs in hadronic Z0 decays

Observation is made of rapidity-alignment of K+K− and pp̄ pairs which results from their asymmetric orientation in rapidity, with respect to the direction from primary quark to antiquark. The K+K− and pp̄ data are consistent with predictions from the fragmentation string model. However, the pp̄ data strongly disagree with the conventional implementation of the cluster model. The non-perturbative process of ‘gluon splitting to diquarks’ has to be incorporated into the cluster model for it to agree with the data. Local conservation of pT between particles nearby in rapidity (i.e., pT compensation) is analysed with respect to the thrust direction for π+π−, K+K−, and pp̄ pairs. In this case, the string model provides fair agreement with the data. The cluster model is incompatible with the data for all three particle pairs. The model with its central premiss of isotropically-decaying clusters predicts a pT correlation not seen in the data.