Related papers: Study of Michel parameters in leptonic $\tau$ deca…
We present the first measurement of the Michel parameters $\bar{\eta}$ and $\xi\kappa$ in the radiative leptonic decay of the $\tau$ lepton using 703 f$\mathrm{b}^{-1}$ of data collected with the Belle detector at the KEKB $e^+e^-$…
The Michel parameters of the leptonic tau decays are measured using the OPAL detector at LEP. The Michel parameters are extracted from the energy spectra of the charged decay leptons and from their energy-energy correlations. A new method…
We present a measurement of the Michel parameters of the $\tau$ lepton, $\bar{\eta}$ and $\xi\kappa$, in the radiative leptonic decay $\tau^- \rightarrow \ell^- \nu_{\tau} \bar{\nu}_{\ell} \gamma$ using 711~f$\mathrm{b}^{-1}$ of collision…
Using the ARGUS detector at the $e^+ e^-$ storage ring DORIS II, we have measured the Michel parameters $\rho$, $\xi$, and $\xi\delta$ for $\tau^{\pm}\to l^{\pm} \nu\bar\nu$ decays in $\tau$-pair events produced at center of mass energies…
We report the first measurement of the Michel parameter $\xi^\prime$ in the $\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau$ decay with a new method proposed just recently. The measurement is based on the reconstruction of the…
Radiative muon and tau lepton decays are described within the model-independent approach with the help of generalized Michel parameters. The exact dependence on charged lepton masses is taken into account. The results are relevant for…
We present the first measurement of the Michel parameter $\xi^\prime$ in the $\tau^-\to\mu^-\bar{\nu}_\mu\nu_\tau$ decay using the full data sample of $988\,\text{fb}^{-1}$ collected by the Belle detector operating at the KEKB asymmetric…
Using the CLEO II detector at the $e^+e^-$ storage ring CESR, we have determined the Michel parameters $\rho$, $\xi$, and $\delta$ in $\tau^\mp \to l^\mp\nu\bar{\nu}$ decay as well as the tau neutrino helicity parameter $h_{\nu_\tau}$ in…
We analyse the effects of Dirac and Majorana neutrinos on leptonic decays of muon and tau leptons using the most general four-lepton effective interaction Hamiltonian of dimension six. We calculate the specific energy and angular…
This paper provides a detailed description of the method for the first direct measurement of all Michel parameters in the $\tau^- \to \mu^- \bar{\nu}_\mu\nu_\tau$ decay related to the polarization of the daughter muon. An application of the…
We present measurements of the tau Michel Parameters made by the CLEO experiment. Three different analyses are performed: a spin-independent lepton spectrum analysis and a second spin-dependent analysis using $\ell^\pm$ \vs\ $\pi^\mp\pi^0$…
We present here the major results obtained in $\tau$ physics by the Belle and Belle II experiments. For the Belle II experiment, we also discuss prospects for improved measurements of the $\tau$ lepton properties, new results in Michel…
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 with the first measurement of the tensor coupling in the weak…
The recent measurements of the Michel parameters in tau decays enable, for the first time, a thorough analysis of the leptonic sector. In general, in models beyond the Standard Model, these parameters will be altered through changes in the…
We derive the decay widths for the leptonic decays of heavy charged pseudoscalars to massive sterile neutrinos, $M^{\pm} \to \ell^{\pm} + N$, within the frameworks involving the Standard Model and two-Higgs doublets (type II). We then apply…
We have searched for lepton-flavor-violating $\tau$ decays with a pseudoscalar meson ($\eta$, $\eta'$ {and} $\pi^0$) using a data sample of 401 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No…
In a recent paper, 8 semileptonic parameters were defined to specify the most general Lorentz-invariant spin correlation functions for 2-body tau decays. These parameters can be used to search for anomalous longitudinal-versus transverse…
We study the $\tau^- \to \nu_{\tau} \pi^{-}\pi^{0}\ell^{+}\ell^{-}$ ($\ell=e,\,\mu$) decays, which are $O(\alpha^2)$-suppressed with respect to the dominant di-pion tau decay channel. Both the inner-bremsstrahlung and the structure- (and…
We have searched for the Lepton Flavor Violating decay $\tau^- \to \mu^- \eta$ using a data sample of 84.3 fb$^{-1}$ accumulated with the Belle detector at KEK. The $\eta$-meson was detected through the decay modes: $\eta \to \gamma\gamma$…
The Michel parameter xi" has been determined from a measurement of the longitudinal polarization of positrons emitted in the decay of polarized and depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is consistent with the…