Long-lived particles (LLPs) could serve as a portal to hidden sectors addressing different open problems of the Standard Model. Among these, the evidence for neutrino masses and mixings—observed in neutrino oscillation experiments—stands out as particularly promising. A simple extension to the SM involves the inclusion of heavy right-handed neutrinos, commonly known as heavy neutral leptons...
In this talk, we revisit a class of lepton-flavor non-universal gauge extensions of the Standard Model that provide a compelling framework for generating neutrino masses and mixing angles via a high-scale seesaw mechanism, while ensuring exact proton stability to all orders in the effective field theory. This setup naturally accommodates minimal thermal leptogenesis, offering a robust...
