  Feebly interacting thermal relics are promising dark matter candidates. Among
them, scenarios of inelastic Dark Matter evade direct detection by suppressed
elastic scattering off atomic nuclei. We introduce inelastic Dirac Dark Matter,
a new model with two Dirac fermions in the MeV-GeV mass range. At feeble
couplings, dark matter can depart from chemical as well as kinetic equilibrium
with the Standard Model before freeze-out. In this case, the freeze-out is
driven by conversion processes like coscattering, rather than coannihilation.
We show that inelastic Dirac relics are consistent with cosmological
observations, in particular with nucleosynthesis and the cosmic microwave
background. Searches for dark sectors at colliders and fixed-target
experiments, in turn, are very sensitive probes. Compared to the strongly
constrained pseudo-Dirac scenario, inelastic Dirac Dark Matter offers a new
search target for existing and upcoming experiments like Belle II, ICARUS, LDMX
and SeaQuest.
