Related papers: Lepton-pair production in di-pion $\tau$ lepton de…
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…
We present the results of a search for charged-lepton-flavor violating decays $\tau^{-} \rightarrow \ell^{-}K_{S}^{0}$, where $\ell^{-}$ is either an electron or a muon. We combine $e^+e^-$ data samples recorded by the Belle II experiment…
Within the Standard Model Effective Field Theory framework, with operators up to dimension 6, we perform a model-independent analysis of the lepton-flavour-violating processes involving tau leptons. Namely, we study hadronic tau decays and…
We search for lepton-flavor-violating tau-> ell V^0 decays, where ell is an electron or muon and V^0 is one of the vector mesons rho^0, phi, omega, K*0 and K*0-bar. We use 854 fb^{-1} of data collected with the Belle detector at the KEKB…
We present the first evidence of the decay B- --> tau- nu_tau-bar using 414 fb^-1 of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. Events are tagged by fully reconstructing…
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…
Tau-lepton decays with up to two $\pi^0$'s in the final state, $\tau^+ \to \pi^+ \bar{\nu}_\tau$, $\rho^+ (\pi^+\pi^0) \bar{\nu}_\tau$, $a^+_1 (\pi^+\pi^0\pi^0) \bar{\nu}_\tau$, are used to study the performance of the barrel part of the…
We present preliminary results of a partial-wave analysis of $\tau^-\to\pi^-\pi^-\pi^+\nu_\tau$ in data from the Belle experiment at the KEKB $\mathrm{e}^+\mathrm{e}^-$ collider. We demonstrate the presence of the $\mathrm{a}_1(1420)$ and…
Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section…
Motivated by models proposed to explain the Standard Model anomalies, and the unprecedented $\tau^{+}\tau^{-}$ data to be collected by the Belle~II experiment during the next years, we study the kinematics of tau pair decays and propose a…
A search for the non-conservation of lepton flavor in the decay tau -> electron gamma has been performed with 2.07 x 10^8 e+e- -> tau+ tau- events collected by the BABAR detector at the PEP-II storage ring at a center-of-mass energy near…
The rare second-class decay mode of the $\tau$ into $\eta\pi\nu$ could be observed for the first time at Belle II. It is important to try to derive a reliable evaluation of the branching fraction and of the energy distribution of this mode…
We report a high-statistics measurement of the branching fraction for tau^- --> pi^- pi^0 nu_tau and the invariant mass spectrum of the produced pi^- pi^0 system using 72.2 fb^-1 of data recorded with the Belle detector at the KEKB…
With the expected large increase in data sets, previously not measured decays will be studied at Belle II. We derive standard model predictions for the $B\to X_u \tau\bar\nu$ decay rate and distributions. The region in the lepton energy…
Experimental studies of B -> D^(*) tau nu decays, are reported. The results are based on large data samples collected at the Upsilon(4S) resonance with the Belle detector at KEKB and the BABAR detector at the SLAC PEP-II asymmetric energy…
The study of the $\tau$-lepton decays into hadrons has contributed to a better understanding of non-perturbative QCD and light-quark meson spectroscopy, as well as to the search of new physics beyond the Standard Model. The two- and…
We present a search for the B- ->tau- nu-bar decay in a data sample of 82 fb^(-1) collected at the Y(4S) resonance with the BaBar detector at the SLAC PEP-II asymmetric B Factory. Continuum and combinatorial backgrounds are suppressed by…
Current and upcoming experiments should improve the sensitivity to radiative lepton decays by an order of magnitude. This paper assumes that one of the tau --> (e, mu) gamma decays is observed, and explores the structure and consequences of…
In this work, we make a study of the $\tau^- \to \omega\pi^-\nu_\tau$ decay in the framework of low-energy effective field theory. The $J^{\mathcal{P}G}$ decompositions of the quark currents and the $\omega\pi$ final state show that,…
Very compelling deviations in the recently observed lepton nonuniversality observables $\big (R_{D^{(*)}}, R_{K^{(*)}}, R_{J/\psi} \big )$ of semileptonic $B$ meson decays from their Standard Model predictions hint towards the presence of…