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Zeitschrift für Physik C
ISSN: 0170-9739 (printed version)
ISSN: 1431-5858 (electronic version)
Abstract Volume 74 Issue 3 (1997) pp 413-422
${\rm B^*}$ production in ${\rm Z^0}$ decays
K. Ackerstaff et al. (8)OPAL Collaboration
(8) CERN, European Organisation for Particle Physics, CH-1211 Geneva 23, Switzerland
Received: 17 December 1996
Abstract. The process ${\rm B}^* \to {\rm B}\gamma$ has been observed in a sample of approximately 4.1 million hadronic ${\rm Z}^0$ decays collected by the OPAL detector at LEP in the years 1991-1995. Inclusively reconstructed B mesons have been combined with converted photons to reconstruct approximately 1900 ${\rm B}^*$ mesons. The ${\rm B}^*$-B mass difference is found to be \[ \Delta M({\rm B}^{*}-{\rm B}) = 46.2 \pm 0.3 \pm 0.8~{\rm MeV}/c^{2}, \] and the rate of ${\rm B}^*$ meson production relative to that of B mesons is found to be \[ \sigma_{\rm B^{*}}/\sigma_{\rm B} = 0.760 \pm 0.036 \pm 0.083, \] where the first errors are statistical and the second systematic. The angular distribution of the transition photon in the ${\rm B}^*$ rest frame has been measured and the relative contribution of longitudinal ${\rm B}^*$ polarization states found to be \[ \sigma_{l}/(\sigma_{l} + \sigma_{t}) = 0.36 \pm 0.06 \pm 0.07, \] consistent with a simple spin counting picture. These results average over B$^{0}$, B$^{\pm}$ and B$^{0}_{\rm s}$ mesons.
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