DOI 10.1007/s100520000407
Transverse and longitudinal
Bose-Einstein correlations
in hadronic Z0 decays
The OPAL Collaboration
G.Abbiendi2 - et al.
2 Dipartimento di Fisica dell' Università di Bologna and INFN,
40126 Bologna, Italy
Received: 3 January 2000 / Published online: 8 June 2000 - © Springer-Verlag 2000
Abstract
Bose-Einstein correlations in pairs of identical charged pions
produced in a sample of 4.3 million Z0 hadronic decays are
studied as a function of the three components of the momentum
difference, transverse ("out" and "side")
and longitudinal with respect to
the thrust direction of the event.
A significant difference between the transverse,
r
tside, and longitudinal, rl, dimensions is observed,
indicating that the emitting source of identical pions, as observed in the
Longitudinally CoMoving System, has an elongated shape.
This is observed with a variety of selection techniques.
Specifically, the values of the parameters obtained by fitting the extended
Goldhaber parametrisation to the correlation function
C' = CDATA/CMCfor two-jet events, selected with the Durham algorithm and
resolution parameter ycut = 0.04, are
r
tside = (0.809 
0.009 (stat)
+0.019-0.032
(syst)) fm,
rl = (0.989 0.011 (stat)
+0.030-0.015 (syst)) fm and rl/r
tside = 1.222 0.027 (stat)
+0.075-0.012 (syst).
The results are discussed in the context of a recent model of
Bose-Einstein correlations based on string fragmentation.
The results of a unidimensional analysis are also presented.
Copyright Società Italiana di Fisica, Springer-Verlag 2000
