Exposing Dark Sector with Future Z-Factories

TL;DR

Future Z-factories at electron-positron colliders could significantly advance dark sector research by probing exotic Z-boson decays with unprecedented sensitivity, complementing other dark matter search methods.

Contribution

This study provides a model-independent analysis of the potential of future Z-factories to detect exotic Z decays across various dark sector models, highlighting their unique sensitivity.

Findings

Sensitivity limits reach as low as 10^{-11} for Tera Z.

Future Z-factories outperform high luminosity LHC in probing exotic decays.

Complementary to other dark matter detection methods.

Abstract

We investigate the prospects of searching dark sector models via exotic Z-boson decay at future $e^+ e^-$ colliders with Giga Z and Tera Z options. Four general categories of dark sector models: Higgs portal dark matter, vector portal dark matter, inelastic dark matter and axion-like particles, are considered. Focusing on channels motivated by the dark sector models, we carry out a model independent study of the sensitivities of Z-factories in probing exotic decays. The limits on branching ratios of the exotic Z decay are typically $\mathcal{O} (10^{-6} - 10^{-8.5}) $ for the Giga Z and $\mathcal{O} (10^{-7.5} - 10^{-11})$ for the Tera Z, and they are compared with the projection for the high luminosity LHC. We demonstrate that future Z-factories can provide its unique and leading sensitivity, and highlight the complementarity with other experiments, including the indirect and direct dark matter search limits, and the existing collider limits. Future Z factories will play a leading role to uncover the hidden sector of the universe in the future.