  Pseudo-Dirac Dark Matter is a viable type of dark matter which originates
from a new Dirac fermion whose two Weyl states get slightly split in mass by a
small Majorana term. The decay of the heavier to the lighter state naturally
occurs over a detectable length scale. Thus, whenever pseudo-Dirac Dark Matter
is produced in a collider, it leaves a clear trace: a visible displaced vertex
in association with missing energy. Moreover, pseudo-Dirac Dark Matter behaves
Dirac-like for relic abundance and Majorana-like in direct detection
experiments: it has efficient s-wave annihilations but it lacks of dangerous
vector interactions with the quarks in the nuclei. We provide a general
treatment using an effective field theory approach, then specializing to the
supersymmetric situation of a pseudo-Dirac Bino. The dark matter mass and the
mass splitting can be extracted from measurements of the decay length and the
invariant mass of the products, even in presence of missing energy.
