  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 ${\cal O}(1)$,
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
which consists of extending the SM 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 flavour violation and DM
in the muon-philic scenario, we analyse 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 9 channels for DM production can be very efficient in testing DM
with masses up to about $1$ TeV.

High Energy Physics - Phenomenology