Search for the dipole portal of heavy neutral leptons at future colliders

TL;DR

This paper evaluates the potential of future colliders like FCC-ee and FCC-hh to detect heavy neutral leptons via the dipole portal, highlighting their complementary capabilities and the extended mass and lifetime reach of FCC-ee.

Contribution

It provides a comparative analysis of collider sensitivities to HNLs through the dipole portal, emphasizing the unique advantages of lepton colliders in this search.

Findings

FCC-ee can probe HNL masses up to ~30 GeV with proper lifetimes >1 cm.

FCC-hh and FCC-ee offer complementary search strategies.

FCC-ee's cleaner environment enhances detection prospects.

Abstract

In this paper, we study the potential of future colliders to explore the parameter space of heavy neutral leptons (HNLs) through the dipole portal. We consider hadron colliders such as the LHC in the high luminosity phase and FCC-hh, and lepton colliders, such as FCC-ee. We consider various signatures for the HNLs, including the missing energy signature and displaced decays, and discuss the complementarity between the hadron and lepton colliders. In particular, we find that thanks to a much clearer environment, FCC-ee may search for the HNLs with masses up to $\simeq 30\text{ GeV}$ and proper lifetimes $c\tau_{N}\gtrsim 1\text{ cm}$, which is well beyond the reach of the experiments to be launched in the next decade.