EPJ

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EPJ C - Particles and Fields
Particles and Fields


Eur. Phys. J. C 20, 401-430 (2001)
DOI: 10.1007/s100520100689

Measurement of the Tau Polarisation at LEP

The ALEPH Collaboration A. Heister and et al.

Physikalisches Institut das RWTH-Aachen, 52056 Aachen, Germany

(Received: 2 March 2001 / Published online: 8 June 2001 -© Springer-Verlag / Società Italiana di Fisica 2001)

Abstract
The polarisation of $\tau$'s produced in Z decay is measured using 160 pb-1 of data accumulated at LEP by the ALEPH detector between 1990 and 1995. The variation of the polarisation with polar angle yields the two parameters ${\cal A}_e = 0.1504 \pm 0.0068 $ and ${\cal A}_{\tau} = 0.1451 \pm 0.0059$ which are consistent with the hypothesis of e-$\tau$ universality. Assuming universality, the value ${\cal A}_{e{-}\tau} = 0.1474 \pm 0.0045$ is obtained from which the effective weak mixing angle $\sin^2 {\theta_{\mathrm{W}}^{\mathrm{eff}}} =0.23147 \pm 0.00057 $ is derived.



© Società Italiana di Fisica, Springer-Verlag 2001

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