Dark matter searches in the mono-$Z$ channel at high energy $e^+e^-$ colliders

TL;DR

This paper investigates the potential of future high-energy electron-positron colliders to detect dark matter via mono-Z signatures, analyzing effective operators, proposing kinematic cuts, and comparing sensitivities with existing indirect searches.

Contribution

It introduces specific kinematic strategies for dark matter detection at colliders and compares collider sensitivities with Fermi-LAT results, highlighting the benefits of beam polarization.

Findings

Collider sensitivity surpasses Fermi-LAT for certain operators.

Polarized beams significantly improve detection significance.

Proposed cuts effectively distinguish signals from backgrounds.

Abstract

We explore the mono-$Z$ signature for dark matter searches at future high energy $e^+e^-$ colliders. In the context of effective field theory, we consider two kinds of contact operators describing dark matter interactions with electroweak gauge bosons and with electron/positron, respectively. For five benchmark models, we propose kinematic cuts to distinguish signals from backgrounds for both charged leptonic and hadronic decay modes of the $Z$ boson. We also present the experimental sensitivity to cutoff scales of effective operators and compare it with that of the Fermi-LAT indirect search and demonstrate the gains in significance for the several configurations of polarized beams.