Collider searches for heavy neutral leptons: beyond simplified scenarios

Abstract With very few exceptions, the large amount of available experimental bounds on heavy neutral leptons – HNL have been derived relying assumption existence a single (usually Majorana) sterile fermion state that mixes with only one lepton flavour. However, most extensions Standard Model involving fermions predict several HNLs, complex mixing patterns to all flavours. Consequently, for HNLs need be recast before being applied generic scenario. In this work, we focus LHC searches and discuss how reinterpret when it comes consider mixings active flavours, not in case HNL, but also more are involved. latter case, possibility interference effects show parameter space should recast.