Bose-Einstein Correlations in $\rm e^+e^-\rightarrow W^+W^-$ at 172 and 183 GeV

Abstract.

Bose-Einstein correlations between like-charge pions are studied in hadronic final states produced by $\mathrme^+\mathrme^-$ annihilations at center-of-mass energies of 172 and 183 GeV. Three event samples are studied, each dominated by one of the processes $\mathrm{W}^+\mathrm{W}^-\rightarrow\mathrm{q\overline{q}}\ell\overline{\nu}_{\ell}$, $\mathrm{W}^+\mathrm{W}^-\rightarrow\mathrm{q\overline{q}}\mathrm{q\overline{q}}$, or $(\mathrm{Z}^0/\gamma)^{*}\rightarrow\mathrm{q\overline{q}}$. After demonstrating the existence of Bose-Einstein correlations in W decays, an attempt is made to determine Bose-Einstein correlations for pions originating from the same W boson and from different W bosons, as well as for pions from $(\mathrm{Z}^0/\gamma)^{*}\rightarrow\mathrm{q\overline{q}}$ events. The following results are obtained for the individual chaoticity parameters $\lambda$, assuming a common source radius R: \begin{eqnarray} \lambda^{\mathrm{ same}} & = & 0.63 \pm 0.19 \pm 0.14 \nonumber , \lambda^{\mathrm{ diff}} & = & 0.22 \pm 0.53 \pm 0.14 \nonumber , \noalign{} \lambda^{\mathrm Z^{*}} & = & 0.47 \pm 0.11 \pm 0.08 \nonumber , R\, & = & 0.92\pm0.09\pm 0.09 \mathrm{fm} \nonumber. \end{eqnarray} In each case, the first error is statistical and the second is systematic. At the current level of statistical precision it is not established whether Bose-Einstein correlations, between pions from different W bosons exist or not.