Searching for Heavy Neutral Leptons with Displaced Vertices at the LHC

Abstract: Heavy Neutral Leptons are naturally present in many well-motivated extensions of the Standard Model. If their mass is of few dozens of GeVs, they can be long-lived and lead to events with displaced vertices, giving rise to promising signatures due to the low background. We revisit the opportunities offered by the LHC to discover these long-lived states via searches with displaced vertices. We study in particular the implication on the parameter space sensitivity when all mixings to active flavors are taken into account.