micro+e- micro-e+ transitions via neutral scalar bosons

Charged Lepton Flavor Violation at the High-Energy Colliders: Neutrino Mass Relevant Particles

We summarize the potential charged lepton flavor violation (LFV) from neutrino mass relevant models, for instance the seesaw mechanisms. In particular, we study, in a model-dependent way, the LFV signals at the high-energy hadron and lepton colliders originating from the beyond standard model (BSM) neutral scalar H, doubly charged scalar H±±, heavy neutrino N, heavy WR boson, and the Z′ boson. For the neutral scalar, doubly charged scalar and Z′ boson, the LFV signals originate from the (effective) LFV couplings of these particles to the charged leptons, while for the heavy neutrino N and WR boson, the LFV effects are from flavor mixing in the neutrino sector. We consider current limits on these BSM particles and estimate their prospects at future high-energy hadron and lepton colliders.

Lepton Flavor Violation Induced by a Neutral Scalar at Future Lepton Colliders

Many new physics scenarios beyond standard model often necessitate the existence of a (light) neutral scalar H, which might couple to the charged leptons in a flavor violating way, while evading all existing constraints. We show that such scalars could be effectively produced at future lepton colliders, either on shell or off shell depending on their mass, and induce lepton flavor violating (LFV) signals, i.e., e^{+}e^{-}→ℓ_{α}^{±}ℓ_{β}^{∓}(+H) with α≠β. We find that a large parameter space of the scalar mass and the LFV couplings can be probed well beyond the current low-energy constraints in the lepton sector. In particular, a scalar-loop induced explanation of the long-standing muon g-2 anomaly can be directly tested in the on-shell mode.