Related papers: Lepton Universality Test in Upsilon(1S) decays at …

We present studies in bottomonium spectroscopy carried out with samples of $(98\pm1)$ million $\Upsilon(2S)$ and $(121\pm1)$ million $\Upsilon(3S)$ events recorded with the BaBar detector at the PEP-II asymmetric-energy $e^+ e^-$ collider…

The experiment NA62 at CERN collected a large sample of K+- leptonic decays in order to perform precise test of lepton universality, by measuring the helicity suppressed ratio R_K=Gamma(K+- --> e+- nu)/Gamma(K+- --> mu+- nu). The…

The Belle and Belle II experiments have collected a 1.4 ab$^{-1}$ sample of $e^+e^-$ collision data at centre-of-mass energies near the $\Upsilon (nS)$ resonances, of which 424 fb$^{-1}$ were collected at Belle II in Run1 (2019--2022). We…

Based on a data sample of 81.7 fb^-1 collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we present the current status of the measurement of the branching fraction of Upsilon(4S)…

One of the key assumptions of the Standard Model of fundamental particles is that the interactions of the charged leptons, namely electrons, muons, and taus, differ only because of their different masses. While precision tests have not…

A test of lepton universality between muons and electrons is performed using $B^+\to K^+\ell^+\ell^-$ decays (where $\ell$ = $e$, $\mu$), in the dilepton invariant-mass-squared region above 14.3 GeV$^2/c^4$. The data used for the…

We present the result from a precision measurement of the mass of the $\tau$ lepton, $M_\tau$, based on $423 fb^{-1}$ of data recorded at the $\Upsilon(4S)$ resonance with the BaBar detector. Using a pseudomass endpoint method, we determine…

The first simultaneous test of muon-electron universality using $B^{+}\rightarrow K^{+}\ell^{+}\ell^{-}$ and $B^{0}\rightarrow K^{*0}\ell^{+}\ell^{-}$ decays is performed, in two ranges of the dilepton invariant-mass squared, $q^{2}$. The…

We study possible effects of a light CP-odd Higgs boson on radiative Upsilon decays in the Next-to-Minimal Supersymmetric Standard Model. Recent constraints from CLEO on radiative Upsilon(1S) decays are translated into constraints on the…

We perform a measurement of the branching fractions for tau -> l gamma nu anti-nu (l= e, mu) decays for a minimum photon energy of 10 MeV in the tau rest frame using 430 fb^-1 of e^+ e^- collisions collected at the center-of-mass energy of…

We search for the rare flavor-changing neutral current process $B^{+}\rightarrow K^{+}\tau^{+}\tau^{-}$ using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the $\Upsilon{(4S)}$ resonance,…

We present the analysis technique and preliminary results of two ongoing analyses at CLEO which put lepton universality and lepton flavor conservation to the test in Upsilon decays.

We present the first measurement of the $B^0\to X_{u}^- \ell^+ {\nu_\ell} $ partial branching fraction in the end-point region of the lepton momentum spectrum, above the threshold for $B\to X_c\ell {\nu_\ell}$ decays. The analysis is based…

The branching fraction $\mathcal{B}(B^0 \to D^{*-}\tau^+\nu_{\tau})$ is measured relative to that of the normalization mode $B^0 \to D^{*-}\pi^+\pi^-\pi^+$ using hadronic $\tau^+ \to \pi^+\pi^-\pi^+(\pi^0)\overline{\nu}_{\tau}$ decays in…

We study inclusive di-pion decays using a sample of 108 x 10^6 Upsilon(3S) events recorded with the BABAR detector. We search for the decay mode Upsilon(3S) --> pi+ pi- h_b(1P) and find no evidence for the bottomonium spin-singlet state…

We present a study of the decays B0bar --> D(*)0 K(*)0bar using a sample of 124 million Upsilon(4S) --> B0bar B0 decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We report evidence for the…

Semileptonic decays provide an excellent environment for testing the Standard Model (SM). Violation of lepton universality would be a smoking gun for physics beyond the SM. Using semi-tauonic $B$ decays, LHCb finds a value of…

A measurement of the ratio of branching fractions $R$(J/$\psi$) = $\mathcal{B}$(B$^+_\text{c}$ $\to$ J/$\psi$$\tau^+\nu_\tau$) / $\mathcal{B}$(B$^+_\text{c}$ $\to$ J/$\psi$$\mu^+\nu_\mu$) in the J/$\psi$ $\to$ $\mu^+\mu^-$, $\tau^+$ $\to$…

The Standard Model of particle physics predicts that charged leptons have the same electroweak interaction strength. This symmetry, called lepton flavour universality, was found to hold in a wide range of particle decays. One observable…

The first test of lepton flavor universality between muons and electrons using $B^+ \to K^+\pi^+\pi^-\ell^+\ell^-$ ($\ell=e,\mu$) decays is presented. The measurement is performed with data from proton-proton collisions collected by the…