  We study the collider signature of pseudo-Dirac heavy neutrinos in the
inverse seesaw scenario, where the heavy neutrinos with mass at the electroweak
scale can have sizable mixings with the Standard Model neutrinos, while
providing the tiny light neutrino masses by the inverse seesaw mechanism. Based
on a simple, concrete model realizing the inverse seesaw, we fix the model
parameters so as to reproduce the neutrino oscillation data and to satisfy
other experimental constraints, assuming two typical flavor structures of the
model and the different types of hierarchical light neutrino mass spectra. With
the fixed parameters in this way, we analyze the heavy neutrino signal at the
LHC through tri-lepton final state with large missing energy and at the ILC
through a single lepton plus di-jet with large missing energy. We find that in
some cases, the heavy neutrino signal can be observed with a large statistical
significance via different flavor charged lepton final states. Therefore, we
can not only discover the heavy neutrinos in the future but also obtain a clue
to reveal the origin of the small neutrino mass and flavor mixing.
