Z-pole test of effective dark matter diboson interactions at the CEPC

TL;DR

This paper assesses CEPC's potential to detect effective dark matter interactions with dibosons at the Z-pole, focusing on semi-visible Z decays and mono-photon signals to improve constraints on dark matter couplings.

Contribution

It provides projected sensitivities for dimension 6 and 7 effective operators involving dark matter and dibosons at CEPC, a novel collider-based approach.

Findings

Projected sensitivity for effective $oldsymbol{ ext{γ}Z}$ coupling is improved.

CEPC can test dark matter couplings beyond current limits.

Sensitivity varies with luminosity and dark matter mass range.

Abstract

In this paper we investigate the projected sensitivity to effective dark matter (DM) - diboson interaction during the high luminosity $Z$-pole and 240 GeV runs at the proposed Circular Electron Positron Collider (CEPC). The proposed runs at the 91.2 GeV $e^+e^-$ center of mass energy offers an interesting opportunity to probe effective dark matter couplings to the $Z$ boson, which can be less stringently tested in non-collider searches. We investigate the prospective sensitivity for dimension 6 and dimension 7 effective diboson operators to scalar and fermion dark matter. These diboson operators can generate semi-visible $Z$ boson decay, and high missing transverse momentum mono-photon signals that can be test efficiently at the CEPC, with a small and controllable Standard Model $\gamma\bar{\nu}\nu$ background. A projected sensitivity for effective $\gamma Z$ coupling efficient $\kappa_{\gamma Z}< (1030$ GeV$)^{-3}$, $(1970$ GeV$)^{-3}$ for scalar DM, $\kappa_{\gamma Z}< (360$ GeV$)^{-3}$, $(540$ GeV$)^{-3}$ for fermion DM are obtain for 25 fb$^{-1}$ and 2.5 ab$^{-1}$ $Z$-pole luminosities assuming the optimal low dark matter mass range. In comparison the effective DM-diphoton coupling sensitivity $\kappa_{\gamma \gamma}< (590$ GeV$)^{-3}$ for scalar DM, $\kappa_{\gamma \gamma}< (360$ GeV$)^{-3}$ for fermion DM are also obtained for a 5 ab$^{-1}$ 240 GeV Higgs run. We also compare the CEPC sensitivities to current direct and indirect search limits on these effective DM-diboson operators.