Lepton portal dark matter at muon colliders: Total rates and generic features for phenomenologically viable scenarios

Lepton portal dark matter (DM) models are a class of models where the DM candidates solely couple to charged leptons through a mediator carrying a lepton number. These models are very interesting since they avoid constraints from direct detection experiments even for coupling of order O(1), they have small annihilation cross sections, and can be probed efficiently at lepton colliders. In this work, we consider a minimal lepton portal DM model that consists of extending the standard model with two SU(2)L singlets: a charged scalar singlet and an electrically neutral right-handed fermion. We systematically study the production mechanisms of DM at multi-TeV muon colliders. After considering all the possible theoretical and experimental constraints and studying the phenomenology of lepton flavor violation and DM in the muonphilic scenario, we analyze the production rates of 54 channels (26 channels for prompt DM production and 28 channels for charged scalar production) at multi-TeV muon colliders. Finally, we discuss the possible collider signatures of some channels and the corresponding backgrounds. We find that at least nine channels for DM production can be very efficient in testing DM with masses up to about 1 TeV.