Search for Z' Radiating from the Dark Matter at the LHC

TL;DR

This paper explores collider signatures of a dark sector with a new Z' gauge boson radiated from dark matter, using dilepton resonance searches at the LHC to constrain the model and propose improved detection strategies.

Contribution

It introduces a novel collider probe of dark matter via Darkstrahlung and refines search strategies to enhance detection sensitivity at the LHC.

Findings

Recast ATLAS and CMS searches to constrain dark matter-Z' coupling.

Propose analysis with invariant mass and missing energy cuts, increasing sensitivity.

Simulation shows up to 6-fold enhancement in detection prospects for low Z' masses.

Abstract

We discuss a collider probe of a dark sector model in which the dark matter is charged under a new, hidden $U(1)$ gauge group. In particular, we look for the so-called Darkstrahlung process, in which the final states dark matter radiates a new $Z'$ gauge boson and it manifests as dilepton resonances. This work emphasizes the potential of dilepton final states with missing transverse energy in probing the darkstrahlung process. We recast the ATLAS Run 2 search for dilepton resonances in association with missing energy in addition to the ATLAS and CMS searches for sleptons. We find that the recasted searches put strong constraints on the coupling between the dark matter and the $Z'$. Moreover, we evaluate refined search strategies for $Z'$ production and propose an analysis employing constraints on the lepton invariant mass and higher missing energy cut related to the darkstrahlung process. Simulation outcomes indicate substantial enhancements, particularly by a factor of 6 in regions featuring lower $Z'$ masses. Finally, we also discuss the case when the $Z'$ has a long lifetime, resulting in displaced decay of the boson.