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Correlation measurements in Z→τ+τ− and the τ neutrino helicity

Research output: Contribution to journalJournal article


<mark>Journal publication date</mark>1994
<mark>Journal</mark>Physics Letters B
Number of pages9
<mark>Original language</mark>English


Using data collected with the ALEPH detector at LEP correlations between the decay products of the τ+ and τ− produced in the decay of the Z have been measured. The measurements performed in the decays τ→πν and τ→ϱν place limits on deviations from the Standard Model. These are given by the parameter ζ with ζ = −1 for the Standard Model. The measured values are ζπ = −0.95 ± 0.11 ± 0.05 and ζϱ = −1.03 ± 0.11 ± 0.05. For models which predict ζπ = ζϱ = ζ — interpreted as the average τ neutrino helicity — the measurement is ζ = −0.99 ± 0.07 ± 0.04.