LAUSR

Heavy lepton singlets N slightly mixed with a standard neutrino νℓ are usually searched for at the LHC in the trilepton plus pTmiss\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {p}_{\textrm{T}}^{\textrm{miss}} $$\end{document} 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.