Reconstructing a Heavy Neutral Lepton at the LHC

Abstract

Heavy lepton singlets N slightly mixed with a standard neutrino νℓ are usually searched for at the LHC in the trilepton plus p miss T channel: pp → W+ → ℓ +N with N → ℓ −W+ → ℓ −ℓ ′+ ν. We show that, although the longitudinal momentum of the final ν escapes detection, the mass of the heavy lepton can be reconstructed. While this possibility has not been considered in recent LHC searches, we find that the search for a mass peak could improve the current collider bounds on the mixing |VℓN | 2 for any mass mN ≥ MW .