Transverse and longitudinal Bose-Einstein correlations

We show how a difference in the correlation length longitudinally and transversely, with respect to the jet axis in e(+)e(-) annihilation, arises naturally in a model for Bose-Einstein correlations based on the Lund string model. In genuine three-particle correlations the difference is even more apparent and they provide therefore a good probe for the longitudinal stretching of the string field. The correlation length between pion pairs is found to be rather independent of the pion multiplicity and the kaon content of the final state. (C) 1998 Elsevier Science B.V.