Zeitschrift für Physik C

ISSN: 0170-9739 (printed version)
ISSN: 1431-5858 (electronic version)

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Abstract Volume 74 Issue 3 (1997) pp 437-449

Study of $\phi(1020)$, ${\rm D}^{*\pm}$ and B$^*$ spin alignment in hadronic Z$^0$ decays

K. Ackerstaff et al. (8)OPAL Collaboration

(8) CERN, European Organisation for Particle Physics, CH-1211 Geneva 23, Switzerland

Received: 10 January 1997

Abstract. Measurements of helicity density matrix elements have been made for the $\phi(1020)$, ${\rm D}^{*\pm}$ and B$^*$ vector mesons in multihadronic Z$^0$ decays in the OPAL experiment at LEP. Results for inclusive $\phi$ produced with high energy show evidence for production preferentially in the helicity zero state, with $\rho_{00} = 0.54 \pm 0.08$, compared to the value of 1/3 expected for no spin alignment. The corresponding element for the ${\rm D}^{*\pm}$ has a value of $0.40 \pm 0.02$, also suggesting a deviation from 1/3. The B$^*$ result, with $\rho_{00} = 0.36 \pm 0.09$, is consistent with no spin alignment. Off-diagonal elements have been measured for the $\phi$ and D$^*$ mesons; for the ${\rm D^*}$ the element ${\rm Re} \rho_{1-1}$ is non-zero, indicating non-independent fragmentation of the primary quarks.

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