Eur. Phys. J. C (2004)

https://doi.org/10.1140/epjc/s2004-01884-3

**36**: 147-159https://doi.org/10.1140/epjc/s2004-01884-3

experimental physics

## Two-dimensional analysis of Bose-Einstein correlationsin hadronic Z decays at LEP

Bose-Einstein correlations are studied in pairs of charged pions from hadronic Z decays, collected by the ALEPH detector. The correlation function, measured using either the unlike-sign or the mixed reference sample, is studied in terms of the Lorentz-invariant four-momentum difference and its transverse, *Q*
_{T}, and longitudinal, *Q*
_{L}, components with respect to the longitudinal centre-of-mass system. Values for the correlation radii, *R*
_{T} and *R*
_{L}, are obtained from the fit of the Goldhaber parametrisation. The results indicate that the correlation radii values depend on the chosen kind of reference sample and on the two-jet purity.

*© Springer-Verlag, 2004*