# A Study of the Lorentz Structure in Tau Decays

Abstract : This paper describes a measurement of the Michel parameters, $\eta$, $\rho$, $\xi$, $\xi \delta$, and the average $\nu_{\tau}$helicity, $h_{\nu_{\tau}}$, in $\tau$ lepton decays together withthe first measurement of the tensor coupling in the weak charged current.The $\tau^{+} \tau^{-}$ pairs were produced at the LEP $\mathrm{e^{+} e^{-}}$collider at CERN from 1992 through 1995 in the DELPHI detector.Assuming lepton universality in the decays of the $\tau$ the measured valuesof the parameters were:$\eta = -0.005 \pm 0.036 \pm 0.037$,$\rho = 0.775 \pm 0.023 \pm 0.020$,$\xi = 0.929 \pm 0.070 \pm 0.030$,$\xi\delta = 0.779 \pm 0.070 \pm 0.028$, $h_{\nu_{\tau}} = -0.997 \pm 0.027 \pm 0.011$.The strength of the tensor coupling was measured to be $\kappa^W_\tau = -0.029\pm 0.036 \pm 0.018$. The first error is statistical and the second erroris systematic in all cases.The results are consistent with the $V\!-\!A$ structure of the weak chargedcurrent in decays of the $\tau$ lepton.
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Journal articles

Cited literature [3 references]

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Submitted on : Wednesday, September 6, 2000 - 11:05:27 AM
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### Citation

P. Abreu, W. Adam, T. Adye, P. Adzic, Z. Albrecht, et al.. A Study of the Lorentz Structure in Tau Decays. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2000, 16, pp.229-252. ⟨10.1007/s100520050017⟩. ⟨in2p3-00005344⟩

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