Neutral and Doubly-Charged Scalars at Future Lepton Colliders

Many new physics scenarios beyond the Standard Model (BSM) necessitate the existence of new neutral and/or charged scalar fields, which might couple to the SM charged leptons (but not hadrons), and thus, can give rise to BSM signals while evading strong constraints mostly coming from the hadronic sector. I show that future lepton colliders provide a clean environment to probe these leptophilic new scalars via multi-lepton final states, including some interesting lepton flavor violating (LFV) channels. I also study the kinematic distributions of the final state leptons to distinguish the BSM contributions from neutral and doubly-charged scalars giving rise to the same final state, as well as from the irreducible SM background.