Related papers: Dark sectors and {\tau} physics at Belle II
The Standard Model (SM) represents our best description of the subatomic world and it has been very successful in explaining how elementary particles interact under the influence of the fundamental forces. Despite its far reaching success…
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…
The Belle II experiment operates at the SuperKEKB asymmetric-energy $e^+e^-$ collider. During the Run 1 data taking, we have collected an integrated luminosity of $424\text{ fb}^{-1}$ of collision data at the energy near the $\Upsilon (4S)$…
We report searches for a new muonic dark force mediated by a gauge boson ($Z'$) coupling only to the second and third lepton families. The existence of the $Z'$ boson is probed in $e^+e^- \to \mu^+\mu^- Z'$, $Z' \to \mu^+ \mu^-$ events,…
In this paper we study the present and future sensitivities of the rare meson decay facilities KOTO, LHCb and Belle II to a light dark sector of the minimal dark abelian gauge symmetry where a dark Higgs $S$ and a dark photon $Z_D$ have…
The rare decays {$B^- \to \tau \bar\nu$}, \mbox{$B \to \tau^+ \tau^-$}, {$b \to X \nu \bar\nu$} and \mbox{$b \to X \tau^+ \tau^-$} all contain third generation leptons in the final state, and hence are sensitive to new physics that couples…
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…
Combining the dark matter and muon $g-2$ anomaly, we study the $U(1)_{L_\mu-L_\tau}$ breaking phase transition, gravitational wave spectra, and the direct detection at the LHC in an extra $U(1)_{L_\mu-L_\tau}$ gauge symmetry extension of…
A possible extension of the Standard Model to include lepton number as local gauge symmetry is investigated. In such a model, anomalies are canceled by two extra fermions doublet. After leptonic gauge symmetry spontaneously broken, three…
We construct a scalar dark matter model with $U(1)_{L_\mu-L_\tau}$ symmetry in which the dark matter interacts with the quark flavours, allowing lepton non-universal $b \to s \ell \bar{\ell}$ decays. The model can solve $b \to s \mu \mu$…
We study charged lepton flavor violation associated with a light leptophilic axion-like particle (ALP), $X$, at the $B$-factory experiment Belle II. We focus on production of the ALP in the tau decays $\tau \to X l$ with $l=e,\mu$, followed…
If physics beyond the Standard Model (BSM) explains the $4.2\sigma$ difference between the Standard-Model and measured muon anomalous magnetic moment, $a_{\mu}$, minimal flavor violation predicts a shift in the analog quantity for the…
We report a measurement of the branching fraction for the leptonic decay $B^+\to\mu^+\nu_\mu$. This work presents the first $B^+\to\mu^+\nu_\mu$ result using Belle~II data, an updated Belle measurement that supersedes the previous result,…
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…
The HyperCP experiment reported the observation of three events for the $\Sigma^+ \rightarrow p \mu^+\mu^-$ decay. The dimuon masses of the observed events are clustered within the detector resolution of 1 MeV/$c^2$. These decays might be…
Some recent $\tau$-physics results are presented from the BaBar and Belle experiments at the SLAC and KEK B factories, which produce copious numbers of $\tau$-lepton pairs. Measurements of the tau mass and lifetime allow to test lepton…
Many models of physics beyond the Standard Model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the Standard Model. We report a search for a dark boson Z' coupling only to…
Lepton flavour violating (LFV) processes are a smoking gun signal of new physics (NP). If the semileptonic $B$ decay anomalies are indeed due to some NP, such operators can potentially lead to LFV decays involving the second and the third…
Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between the two dark matter particles…
Several models of particle physics different from the Standard Model predict the existence of a dark sector that is weakly coupled to the visible one: the two sectors may couple via the vector portal, where a dark photon with mass in the…