Heavy Neutrinos at the FCC-hh in the $U(1)_{B-L}$ Model

TL;DR

This paper explores the potential of the FCC-hh collider to detect heavy neutrinos through a $U(1)_{B-L}$ gauge boson, highlighting the importance of prompt and displaced decay searches for different mass ranges.

Contribution

It introduces a detailed analysis of heavy neutrino production via a $U(1)_{B-L}$ $Z'$ at 100 TeV, comparing prompt and displaced decay search strategies and their sensitivities.

Findings

TeV-scale heavy neutrinos can be probed for a 5 TeV $Z'$ with small gauge coupling.

Displaced vertex searches extend sensitivity to neutrino masses as low as 10 GeV.

Prompt semi-leptonic modes offer better detection prospects due to lower background.

Abstract

We investigate the potential of the 100 TeV future circular collider (FCC-hh) to probe heavy neutrinos. We concentrate in particular on heavy neutrino production via a $U(1)_{B-L}$ $Z'$ gauge boson and contrast the resulting limits with that mediated by Standard Model weak currents. We consider heavy neutrino decays to semi-leptonic as well as fully leptonic final states, particularly with muon flavour, and we show the importance of considering searches both in prompt and displaced decays of the heavy neutrinos. For prompt final states, semi-leptonic modes are more promising due to smaller background and larger yields, and TeV-scale heavy neutrinos with active-sterile mixing compatible with light neutrino mass generation in a seesaw scenario can be probed for a 5 TeV $Z'$ and gauge coupling as low as $g_{B-L} = 10^{-2}$. Displaced vertex searches can extend this range to heavy neutrino masses as low as 10 GeV.