Improved constraints and the prospects of detecting TeV to PeV scale Heavy Neutral Leptons

Heavy neutral leptons (HNLs) are hypothetical particles able to explain neutrino oscillations and provide a mechanism for generating the baryon asymmetry of the Universe. Quantum corrections due to such particles give rise to lepton flavor violating processes involving charged Standard Model leptons. Using the fact that these corrections grow with HNL masses, we improve existing constraints by orders of magnitude in mass and in interaction strength. This allows us to probe part of the parameter space of leptogenesis with multi-TeV HNLs. We also show that one will be able to infer HNL parameters in a significant portion of the parameter space for TeV-PeV masses if lepton flavor violating signals are detected.