Multiplicity dependence of Bose-Einstein correlations in hadronic Z⁰ decays

Abstract

Bose-Einstein correlations between like charged track pairs have been studied using a sample of approximately 3.6 million multihadronic Z⁰ decays collected with the OPAL detector at LEP. The radius of the emitting sourceR and the chaoticity parameterλ were studied using two parametrisations, the Goldhaber (G) parametrisation and the one-dimensional Kopylov-Podgoretskii (KP) parametrisation. The radiiR _G andR _KP are found to increase linearly with the average observed charged multiplicityn _ch , with changes with respect to a unit increase inn _ch of

$$\begin{gathered} \frac{1}{{\langle R_G \rangle }}\frac{{\Delta R_G }}{{\Delta n_{ch} }} = (3.6 \pm 0.6) \cdot 10^{ - 3} and \hfill \\ \frac{1}{{\langle R_{KP} \rangle }}\frac{{\Delta R_{KP} }}{{\Delta n_{ch} }} = (3.4 \pm 1.0) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$

where the 〈R〉 are the radius values measured in the inclusive event sample. The chaoticity parametersλ _G andλ _KP decrease with increasing charged multiplicity. It is shown that the increase ofR with multiplicity may be connected with differences between two- and three-jet events.