Related papers: Lepton Universality, |V_{us}| and search for secon…

We present a measurement of the $\tau$-lepton mass using a sample of about 175 million $e^+e^- \to \tau^+\tau^-$ events collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider at a center-of-mass energy of…

We have performed a search for the rare leptonic decay B+ --> mu+ nu_mu with data collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II storage ring. In a sample of 88.4 million BBbar pairs, we find no significant…

The Standard Model of particle physics encapsulates our current best understanding of physics at the smallest scales. A fundamental axiom of this theory is the universality of the couplings of the different generations of leptons to the…

We use experimental data on $e^+e^- \to \eta (\eta^{\prime})\pi^+\pi^-$ and conservation of vector current to estimate the branching fractions of $\tau^-$ decay to $\eta (\eta^{\prime})\pi^-\pi^0\nu_{\tau}$. The obtained values are compared…

Tests of lepton universality in $B^0\to K^0_S \ell^+ \ell^-$ and $B^+\to K^{*+} \ell^+ \ell^-$ decays where $\ell$ is either an electron or a muon are presented. The differential branching fractions of $B^0\to K^0_S e^+ e^-$ and $B^+\to…

I present two analyses done with the CLEOIII detector at CESR. The first is a search for the Lepton Flavor Violating decay Upsilon to mu tau, with preliminary results, and the second constrains Lepton Universality in Upsilon to tau tau…

KLOE has measured most decay branching ratios of Ks, Kl and K+/- mesons. It has also measured the Kl and the K+- lifetime and determined the shape of the form factors involved in kaon semileptonic decays. We present in the following a…

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…

Using a sample of (470.9 +- 2.8) x 10^6 BB-bar pairs, we measure the decay branching fraction B(B^0 -> D^*- pi^+ pi^- pi^+) = (7.26 +- 0.11 +- 0.31) x 10^-3, where the first uncertainty is statistical and the second is systematic. Our…

The pure leptonic or semileptonic character of tau decays makes them a good laboratory to test the structure of the weak currents and the universality of their couplings to the gauge bosons. The hadronic tau decay modes constitute an ideal…

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 search for the purely leptonic decay $B^{\pm} \to \mu^{\pm} \nu_{\mu}$ in the full BaBar dataset, having an integrated luminosity of approximately 426 fb$^{-1}$. We adopt a fully inclusive approach, where the signal candidate is…

Using data collected with the L3 detector near the Z resonance, corresponding to an integrated luminosity of 150pb-1, the branching fractions of the tau lepton into electron and muon are measured to be B(tau->e nu nu) = (17.806 +- 0.104…

Motivated by the recent investigation of neutrinoless $\tau$-lepton decays by the CLEO collaboration, we perform a systematic analysis of such decays in a possible new-physics scenario with heavy Dirac/Majorana neutrinos, including…

Tau lepton decays with open strangeness in the final state are measured with the OPAL detector at LEP to determine the strange hadronic spectral function of the tau lepton. The decays T- ->(Kpi)-nu tau, (Kpipi)-nu tau and (Kpipipi) -nu tau…

The ratio of branching fractions ${\cal{R}}(D^{*-})\equiv {\cal{B}}(B^0 \to D^{*-} \tau^+ \nu_{\tau})/{\cal{B}}(B^0 \to D^{*-} \mu^+\nu_{\mu})$ is measured using a data sample of proton-proton collisions collected with the LHCb detector at…

Kaon experiments are now focusing on searching for new physics beyond the standard model. For example, CERN NA62, J-PARC KOTO and J-PARC TREK-E36 experiments are starting up to study K->pi nu nu-bar decay modes, a lepton flavor violation,…

We present a search for the decays B0->e+e-, B0->mu+mu-, and B0->emu in data collected at the Upsilon(4S) with the BABAR detector at the SLAC B Factory. Using a data set of 54.4 fb-1, we find no evidence for a signal and set the following…

The DONUT collaboration has observed four events in a hybrid emulsion spectrometer consistent with tau neutrino charged-current interactions. The resulting tau lepton is identified by its decay into a single charged particle. The expected…

The branching ratios of the decay of the tau lepton to five charged hadrons have been measured with the OPAL detector at LEP using data collected between 1991 and 1995 at e+e- centre-of-mass energies close to the Z resonance. The branching…