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We construct an expression for a general lepton flavour universality (LFU) ratio, $R_{X}$, in $b\to s l^+ l^-$ decays in terms of a series of hadronic quantities which can be treated as nuisance parameters. This expression allows to include…

High Energy Physics - Phenomenology · Physics 2022-06-01 Gino Isidori , Davide Lancierini , Abhijit Mathad , Patrick Owen , Nicola Serra , Rafael Silva Coutinho

Recently, several new experimental results of the test of lepton flavor universality (LFU) in $B\to D^{(\ast)}$ semi-leptonic decays were announced: the first result of $R_{D}$ from the LHCb Run 1 data, the first results of $R_{D}$ and…

High Energy Physics - Phenomenology · Physics 2024-10-11 Syuhei Iguro , Teppei Kitahara , Ryoutaro Watanabe

Lepton flavor violation is one of the cleanest probes of physics beyond the standard model. In this work, we explore the sensitivity of the process $e^+ e^- \to \tau \mu$ to new physics above the TeV scale at the proposed circular…

High Energy Physics - Phenomenology · Physics 2023-05-09 Wolfgang Altmannshofer , Pankaj Munbodh , Talise Oh

We report on the first searches for lepton flavour violating $\tau^-$ decays at a hadron collider. These include searches for the lepton flavour violating decay $\tau^-\to \mu^+\mu^-\mu^-$ and the lepton flavour and baryon number violating…

High Energy Physics - Experiment · Physics 2015-09-08 Jonathan Harrison

We investigate a gauge extension of the Standard Model in light of the observed hints of lepton universality violation in $b \to c \ell \nu$ and $b \to s \ell^+ \ell^-$ decays at BaBar, Belle and LHCb. The model consists of an extended…

High Energy Physics - Phenomenology · Physics 2016-12-19 Sofiane M. Boucenna , Alejandro Celis , Javier Fuentes-Martin , Avelino Vicente , Javier Virto

We present an overview of searches fo violation of lepton flavor universality with focus on low energy precision probes using pions, kaons, tau leptons, and nuclear beta decays. The current experimental results are reviewed, the theoretical…

High Energy Physics - Phenomenology · Physics 2022-10-12 Douglas Bryman , Vincenzo Cirigliano , Andreas Crivellin , Gianluca Inguglia

We present a complete analysis of Lepton Flavor Universality (LFU) violations in leptonic $\tau$ decays in motivated models addressing the $B$-physics anomalies, based on the $SU(4)\times SU(3)\times SU(2)\times U(1)$ gauge group. We show…

High Energy Physics - Phenomenology · Physics 2022-01-19 Lukas Allwicher , Gino Isidori , Nudzeim Selimovic

Lepton flavor violation (LFV) is studied within a realistic unified framework, based on supersymmetric SO(10) or an effective G(224) = SU(2)_L\times SU(2)_R\times SU(4)^c symmetry, that successfully describes (i) fermion masses and mixings,…

High Energy Physics - Phenomenology · Physics 2014-11-18 K. S. Babu , Jogesh C. Pati , Parul Rastogi

In the Standard Model of particle physics, lepton flavour and lepton number are conserved quantities although no fundamental symmetry demands their conservation. I present recent results of searches for lepton flavour and lepton number…

High Energy Physics - Experiment · Physics 2012-09-25 Paul Seyfert

Lepton Flavour Universality tests with semileptonic $\Lambda_b\to\Lambda_c^*$ decays are important to corroborate the present anomalies in the similar ratios $R_{D^{(*)}}$, and can provide complementary constraints on possible origins of…

High Energy Physics - Phenomenology · Physics 2018-07-31 Philipp Böer , Marzia Bordone , Elena Graverini , Patrick Owen , Marcello Rotondo , Danny van Dyk

The conservation of lepton flavor is a prediction of the Standard Model and is still an excellent approximate symmetry despite our observation of neutrino oscillations. Lepton flavor violation by one or two units have been discussed for…

High Energy Physics - Phenomenology · Physics 2025-09-30 Julian Heeck , Mikheil Sokhashvili , Anil Thapa

In the coming years, experiments underway will increase the sensitivity to charged lepton flavor violation by four orders of magnitude. These experiments will stringently probe weak scale physics. I review the status of global symmetries in…

High Energy Physics - Phenomenology · Physics 2017-08-23 Jonathan L. Feng

Lepton Flavor Violating (LFV) processes are clear signals of physics beyond the Standard Model. We investigate the possibility of measuring this kind of processes at present and foreseeable future muon-electron colliders, taking into…

High Energy Physics - Phenomenology · Physics 2020-12-15 Fabio Bossi , Paolo Ciafaloni

Anomalies in (semi)leptonic $B$-meson decays present interesting patterns that might be revealing the shape of the new physics to come. In order to understand the experimental data, we explore symmetry arguments that lead to the hypothesis…

High Energy Physics - Phenomenology · Physics 2015-05-21 Rodrigo Alonso , Benjamín Grinstein , Jorge Martin Camalich

Here I review the status and prospects of experimental investigations into lepton flavor violation (LFV) in charged leptons. Rare LFV processes are naturally expected to occur through loops of TeV scale particles predicted by supersymmetric…

High Energy Physics - Experiment · Physics 2008-11-26 Toshinori Mori

Lepton Flavor Universality Violation (LFUV) in $B$ decays in both neutral $b\rightarrow s l^+ l^-$ and charged $b\rightarrow cl\bar{\nu}_{l}$ processes observed in the ratios $R_{K^{(*)}}$ and $R_{D^{(*)}}$ is investigated in the framework…

High Energy Physics - Phenomenology · Physics 2022-02-16 Soumia Lebbal , Jamal Mimouni , Noureddine Mebarki

Measurements of lepton flavor universality (LFU) and searches for charged lepton flavor violation (cLFV) are one of the most straightforward ways of searching for Beyond Standard Model (BSM) physics. The numerous production of top quark…

High Energy Physics - Experiment · Physics 2026-01-08 Normunds Ralfs Strautnieks

Lepton flavor violations in charged lepton give good signatures for the new physics. We review recent searches for lepton flavor violation in tau decays at B-factories. In these searches, optimization for background reduction is important…

High Energy Physics - Experiment · Physics 2011-09-22 Yoshiyuki Miyazaki

In view of recent experimental indications of violations of Lepton Flavor Universality (LFU) in $B$ decays, we analyze constraints and implications of LFU interactions, both using an effective theory approach, and an explicit dynamical…

High Energy Physics - Phenomenology · Physics 2015-07-03 Admir Greljo , Gino Isidori , David Marzocca

A sensitivity study for the search for the charged lepton flavor violating process $\tau \to \gamma\mu$ at the Super $\tau$-Charm Facility is performed with a fast simulation. With the expected performance of the current detector design and…

High Energy Physics - Experiment · Physics 2023-10-17 Teng Xiang , Xiao-Dong Shi , Da-Yong Wang , Xiao-Rong Zhou