Testing Lepton Flavor Universality with Pion, Kaon, Tau, and Beta Decays

Abstract

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 status within the context of the Standard Model is summarized, and future prospects (both experimental and theoretical) are discussed. We review the implications of these measurements for physics beyond the Standard Model by performing a global model-independent fit to modified $W$ couplings to leptons and four-fermion operators. We also discuss new physics in the context of simplified models and review Standard Model extensions with focus on those which can explain a possible deviation from unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

33 pages, 2 figures, invited contribution to "Annual Review of Nuclear and Particle Science"

References in corpus (23)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm
• Search for lepton-universality violation in $B^{+}\to K^{+}{\ell }^{+}{\ell }^{-}$ decays
• Effects of new leptons in Electroweak Precision Data
• Measurement of the Weak Axial-Vector Coupling Constant in the Decay of Free Neutrons Using a Pulsed Cold Neutron Beam
• Limiting two-Higgs-doublet models
• The Standard Model prediction for R_{e/mu}^{(pi,K)}
• Prospects for the Zee-Babu Model at the LHC and low energy experiments
• Constraints on Sterile Neutrinos in the MeV to GeV Mass Range
• pi/K -> e nu branching ratios to O(e^2 p^4) in Chiral Perturbation Theory
• Revising Limits on Neutrino-Majoron Couplings
• Search for heavy neutral lepton production in $K^{+}$ decays to positrons
• First-principles calculation of electroweak box diagrams from lattice QCD
• Search for $K^{+}$ decays to a muon and invisible particles
• Electromagnetic effects in Kl3 decays
• A Minimal Explanation of Flavour Anomalies: B-Meson Decays, Muon Magnetic Moment, and the Cabibbo Angle
• A Class of Three-Loop Models with Neutrino Mass and Dark Matter
• Testing Radiative Neutrino Mass Models at the LHC
• Mounting Evidence for the Violation of Lepton Flavor Universality
• Pion Leptonic Decays and Supersymmetry
• Experimental study of rare charged pion decays
• Upper limits on branching ratios of the lepton-flavor-violating decays $\tau \to \ell \gamma \gamma$ and $\tau \to \ell X$

Cited by in corpus (17)

• Global Fit of Modified Quark Couplings to EW Gauge Bosons and Vector-Like Quarks in Light of the Cabibbo Angle Anomaly
• One-loop determination of $\tau \to \pi (K){\nu }_{\tau }[\gamma ]$ branching ratios and new physics tests
• Flavor Physics at the CEPC: a General Perspective
• Minimal model for the $W$-boson mass, $(g-2{)}_{\mu }$, $h\to {\mu }^{+}{\mu }^{-}$ and quark-mixing-matrix unitarity
• The $W\ell \nu$-vertex corrections to W-boson mass in the R-parity violating MSSM
• Explaining anomalies of $B$-physics, muon $g-2$ and $W$ mass in $R$-parity violating MSSM with seesaw mechanism
• The Low-Scale Seesaw Solution to the $M_W$ and $(g-2{)}_{\mu }$ Anomalies
• Leptonic neutral-current probes in a short-distance DUNE-like setup
• Study of the muon decay-in-flight in the ${\tau }^{-}\to {\mu }^{-}{\bar{\nu }}_{\mu }{\nu }_{\tau }$ decay to measure the Michel parameter ${\xi }^{\prime }$
• MeV Sterile Neutrino in light of the Cabibbo-Angle Anomaly
• Machine Learning Approaches to Top Quark Flavor-Changing Four-Fermion Interactions in Trilepton Signals at the LHC
• Theoretical point of view on Cabibbo angle anomaly
• Test of light-lepton universality in $\tau$ decays with the Belle II experiment
• Explaining the $B_{d(s)}\to K^{(\ast )}{\bar{K}}^{(\ast )}$ puzzle via chiral-flip in $R$-parity violating MSSM with seesaw mechanism
• Branching fraction measurement of the $\Lambda \to p{\mu }^{-}{\overline{\nu }}_{\mu }$ decay
• Riding the Seesaw: What Higgsstrahlung May Reveal about Massive Neutrinos
• Computing one-loop radiative corrections in $\tau \to \pi (K)\nu [\gamma ]$ and testing new physics