Multilepton dark matter signals

TL;DR

This paper explores multilepton signals from dark matter scenarios involving a $Z'$ boson and dark leptons, proposing a promising four-lepton signature detectable at current and future colliders.

Contribution

It identifies a novel four-lepton signature from $Z'$-portal dark matter models with dark leptons and estimates collider sensitivities for this signal.

Findings

Four-lepton signals can reach 5σ significance at LHC Run 2.

Future colliders can probe couplings two orders of magnitude smaller.

Multilepton signatures are promising for dark matter detection at colliders.

Abstract

The signatures of dark matter at the LHC commonly involve, in simplified scenarios, the production of a single particle plus large missing energy, from the undetected dark matter. However, in $Z'$-portal scenarios anomaly cancellation requires the presence of extra dark leptons in the dark sector. We investigate the signatures of the minimal scenarios of this kind, which involve cascade decays of the extra $Z'$ boson into the dark leptons, identifying a four-lepton signal as the most promising one. We estimate the sensitivity to this signal at the LHC, the high-luminosity LHC upgrade, a possible high-energy upgrade, as well as a future circular collider. For $Z'$ couplings compatible with current dijet constraints the multilepton signals can reach the $5\sigma$ level already at Run 2 of the LHC. At future colliders, couplings two orders of magnitude smaller than the electroweak coupling can be probed with $5\sigma$ sensitivity.