Lepton Flavor Violation with Displaced Vertices

Abstract

If light new physics with lepton-flavor-violating couplings exists, the prime discovery channel might not be $\ell \to {\ell }^{\prime }\gamma$ but rather $\ell \to {\ell }^{\prime }X$, where the new boson $X$ could be an axion, majoron, familon or Z' gauge boson. The most conservative bound then comes from $\ell \to {\ell }^{\prime }+\mathrm{inv}$, but if the on-shell $X$ can decay back into leptons or photons, displaced-vertex searches could give much better limits. We show that only a narrow region in parameter space allows for displaced vertices in muon decays, $\mu \to eX,X\to \gamma \gamma ,ee$, whereas tauon decays can have much more interesting signatures.

7 pages, to appear in PLB

References in corpus (16)

• Search for a dark photon in e+e- collisions at BABAR
• Light Dark Matter: Models and Constraints
• Stellar cooling bounds on new light particles: plasma mixing effects
• Revised constraints and Belle II sensitivity for visible and invisible axion-like particles
• Flaxion: a minimal extension to solve puzzles in the standard model
• Discovering New Light States at Neutrino Experiments
• Lepton flavor violating Z' explanation of the muon anomalous magnetic moment
• Higgs $\to \mu \tau$ in Abelian and Non-Abelian Flavor Symmetry Models
• MEG Upgrade Proposal
• Cold keV dark matter from decays and scatterings
• A search for two body muon decay signals
• Projections for Dark Photon Searches at Mu3e
• An invisible axion model with controlled FCNCs at tree level
• Interpretation of Lepton Flavor Violation
• A class of invisible axion models with FCNCs at tree level
• Systematic Study Of Leptonic Mixing In A Class Of SU_H(2) Models

Cited by in corpus (5)

• Searching for axionlike particle at future $ep$ colliders
• Upper limits on branching ratios of the lepton-flavor-violating decays $\tau \to \ell \gamma \gamma$ and $\tau \to \ell X$
• Exotic Lepton-Flavor Violating Higgs Decays
• A search for a cosmologically-relevant boson in muon decay
• Searching for Charged Lepton Flavour Violation with Mu3e