Displaced heavy neutrinos from $Z^{\prime }$ decays at the LHC

Abstract

We study the LHC sensitivity to probe a long-lived heavy neutrino $N$ in the context of $Z^{\prime }$ models. We focus on displaced vertex signatures of $N$ when pair produced via a $Z^{\prime }$, decaying to leptons and jets inside the inner trackers of the LHC experiments. We explore the LHC reach with current long-lived particle search strategies for either one or two displaced vertices in association with hadronic tracks or jets. We focus on two well-motivated models, namely, the minimal $U(1{)}_{B-L}$ scenario and its $U(1{)}_X$ extension. We find that searches for at least one displaced vertex can cover a significant portion of the parameter space, with light-heavy neutrino mixings as low as $|V_{lN}{|}^2\approx 10^{-17}$, and $l=e,\mu$ accessible across GeV scale heavy neutrino masses.

Comments: 25 pages, 11 figures. In v2: added references and eta cut for electrons. Figures modified, results unchanged. Version accepted for publication in JHEP