Inverse Seesaw Neutrino Signatures at LHC and ILC

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.