Right handed neutrino production from $Z^\prime$ interactions in forward search experiments

TL;DR

This paper investigates the production of right-handed neutrinos via a new $Z'$ gauge boson in extended $U(1)$ models, analyzing detection prospects at HL-LHC and FASER2 with projected experimental limits.

Contribution

It introduces a comprehensive analysis of right-handed neutrino production from $Z'$ decays in two $U(1)$ extension scenarios, focusing on detection strategies at future collider experiments.

Findings

Projected limits on $U(1)$ gauge coupling and $Z'$ mass.

Constraints on right-handed neutrino properties.

Comparison with current experimental bounds.

Abstract

We study two general $U(1)$ extensions of the Standard Model (SM) those generate tiny neutrino masses via the seesaw mechanism after general $U(1)$ breaking. These models predict a new neutral gauge boson ($Z'$) and right-handed neutrinos (RHNs), the latter introduced for anomaly cancellation and neutrino mass generation. In both scenarios, left- and right-handed fermions couple differently to the $Z'$, and RHNs mix with light neutrinos, enabling variety of decay modes. Focusing on the high-luminosity LHC (HL-LHC) and the future FASER2 experiment, we explore RHN pair production from $Z'$ decays in two cases: (i) long-lived $Z'$ decays to visible modes and long-lived RHNs, and (ii) short-lived $Z'$ decays to long-lived RHNs, which further decay visibly inside FASER2. We estimate projected limits on the general $U(1)$ gauge coupling, $Z'$ mass, RHN mass, and light-heavy neutrino mixing for various $U(1)$ charge assignments, and compare them with current experimental bounds.