Collider testable seesaw models predict pseudo-Dirac heavy neutral leptons. These almost mass degenerate pairs of heavy Majorana neutrinos can oscillate between neutrino and anti-neutrino eigenstates. Exploiting long-lived decay signatures, such oscillations can be observed in a modulation between lepton number conserving and violating processes. I present a minimal model capturing the phenomenology of lepton number violation in type I seesaw models and its FeynRules implementation. Additionally, I show how to extend MadGraph to be able to simulate such oscillations and present chosen example results.
With support from FCT through project UIDB/00777/2020