Testing Higgs portal dark matter via $Z$ fusion at a linear collider

TL;DR

This paper explores the potential to detect Higgs portal dark matter particles at future linear colliders through Z boson fusion processes, especially when direct Higgs decays to dark matter are kinematically forbidden.

Contribution

It demonstrates that Z fusion processes at TeV-scale linear colliders can probe dark matter masses up to 100 GeV in Higgs portal scenarios, even when Higgs decays to dark matter are not accessible.

Findings

Signal detectable at √S > 1 TeV with 1 ab^{-1} luminosity

Dark matter masses up to 100 GeV can be tested for Higgs mass 120 GeV

Effective for fermion and vector dark matter candidates

Abstract

We investigate the possibility of detecting dark matter at TeV scale linear colliders in the scenario where the dark matter is a massive particle weakly interacting only with the Higgs boson $h$ in the low energy effective theory (the Higgs portal dark matter scenario). The dark matter in this scenario would be difficult to be tested at the CERN Large Hadron Collider when the decay of the Higgs boson into a dark matter pair is not kinematically allowed. We study whether even in such a case the dark matter $D$ can be explored or not via the $Z$ boson fusion process at the International Linear Collider and also at a multi TeV lepton collider. It is found that for the collision energy $\sqrt{S}>1$ TeV with the integrated luminosity 1 ab$^{-1}$, the signal ($e^{\pm}e^-\to e^{\pm}e^-h^\ast \to e^{\pm}e^-DD$) can be seen after appropriate kinematic cuts. In particular, when the dark matter is a fermion or a vector, which is supposed to be singlet under the standard gauge symmetry, the signal with the mass up to 100 GeV can be tested for the Higgs boson mass to be 120 GeV.