Elsevier, Physics Letters B, 4(458), p. 517-528, 1999
DOI: 10.1016/s0370-2693(99)00662-0
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We measure Bose-Einstein correlations between like-sign charged pion pairs in hadronic Z decays with the L3 detector at LEP. The analysis is performed in three dimensions in the longitudinal center-of-mass system. The pion source is found to be elongated along the thrust axis with a ratio of transverse to longitudinal radius of 0.81 +/- 0.02(-0.19)(+0.03). (C) 1999 Published by Elsevier Science B.V. All rights reserved.