LHC Dark Matter Signals from Vector Resonances and Top Partners

TL;DR

This paper investigates how a vector resonance $Z'$ can enhance dark matter and top partner signals at the LHC, providing new avenues for detection beyond existing bounds, with implications for TeV-scale physics.

Contribution

It introduces a simplified effective model with a $Z'$, top partner $T'$, and scalar DM, analyzing their collider phenomenology and revealing the $Z'$'s significant role in LHC searches.

Findings

$Z'$ enhances $T'$ and DM detection prospects at the LHC.

LHC probes DM masses up to 900 GeV and top partners up to 1.5 TeV.

The $Z'$ contribution exceeds QCD production bounds by nearly a factor of two.

Abstract

Extensions of the Standard Model which address the hierarchy problem and dark matter (DM) often contain top partners and additional resonances at the TeV scale. We explore the phenomenology of a simplified effective model with a vector resonance $Z'$, a fermionic vector-like coloured partner of the top quark $T'$ as well as a scalar DM candidate $\phi$ and provide publicly available implementations in CalcHEP and MadGraph. We study the $pp \to Z' \to T'\overline{T'} \to t\bar{t}\,\phi\phi$ process at the LHC and find that it plays an important role in addition to the $T'\overline{T'}$ production via strong interactions. It turns out that the presence of the $Z'$ can provide a dominant contribution to the $t\bar{t}+E_T^{\text{miss}}$ signature without conflicting with existing bounds from $Z'$ searches in di-jet and di-lepton final states. We find that through this process, the LHC is already probing DM masses up to about 900 GeV and top partner masses up to about 1.5 TeV, thus exceeding the current bounds from QCD production alone almost by a factor of two for both particles.