Displaced heavy neutrinos from $Z'$ decays at the LHC

TL;DR

This paper investigates the LHC's ability to detect long-lived heavy neutrinos produced from $Z'$ decays, focusing on displaced vertex signatures in specific $U(1)$ models, and finds promising sensitivity for very small neutrino mixings.

Contribution

It introduces a detailed analysis of displaced vertex signatures for heavy neutrinos in $Z'$ models, extending current search strategies and exploring new parameter space.

Findings

Displaced vertex searches can probe neutrino mixings as low as 10^{-17}.

Significant portions of parameter space are accessible for GeV-scale heavy neutrinos.

Current strategies are effective for detecting long-lived neutrinos in specific $U(1)$ models.

Abstract

We study the LHC sensitivity to probe a long-lived heavy neutrino $N$ in the context of $Z'$ models. We focus on displaced vertex signatures of $N$ when pair produced via a $Z'$, 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.