Searching for Dark Matter at the LHC with a Mono-Z

TL;DR

This paper explores using mono-Z events at the LHC as a novel method to detect dark matter, highlighting its potential to complement existing search strategies through distinctive electroweak signatures.

Contribution

It introduces a mono-Z search strategy for dark matter at the LHC, demonstrating its feasibility and potential to discover or provide additional insights into the dark sector.

Findings

Mono-Z signatures can be distinguished from Standard Model backgrounds with modest cuts.

Certain parameter regions show clear signals above background in future LHC data.

Mono-Z searches can complement existing dark matter detection channels.

Abstract

We investigate a mono-Z process as a potential dark matter search strategy at the LHC. In this channel a single Z boson recoils against missing transverse momentum, attributed to dark matter particles, $\chi$, which escape the detector. This search strategy is related, and complementary to, monojet and monophoton searches. For illustrative purposes we consider the process $q\bar{q} -> \chi\chi Z$ in a toy dark matter model, where the Z boson is emitted from either the initial state quarks, or from the internal propagator. Among the signatures of this process will be a pair of muons with high pT that reconstruct to the invariant mass of the Z, and large amounts of missing transverse energy. Being a purely electroweak signal, QCD and other Standard Model backgrounds are relatively easily removed with modest selection cuts. We compare the signal to Standard Model backgrounds and demonstrate that, even for conservative cuts, there exist regions of parameter space where the signal may be clearly visible above background in future LHC data, allowing either new discovery potential or the possibility of supplementing information about the dark sector beyond that available from other observable channels.