Search for dark matter in events with a hadronically decaying vector boson and missing transverse momentum in $pp$ collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

TL;DR

This paper reports a search for dark matter particles produced with hadronically decaying vector bosons in proton-proton collisions at 13 TeV using ATLAS data, setting limits on various dark matter production models.

Contribution

It introduces an improved analysis with larger dataset and optimized selection, and explores a new mono-$Z'$ channel for dark matter production, extending previous searches.

Findings

No significant excess observed over Standard Model predictions.

Set limits on invisible Higgs decays to dark matter.

Constrained parameter space of simplified vector-mediator models.

Abstract

A search for dark matter (DM) particles produced in association with a hadronically decaying vector boson is performed using $pp$ collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV corresponding to an integrated luminosity of 36.1 fb$^{-1}$, recorded by the ATLAS detector at the Large Hadron Collider. This analysis improves on previous searches for processes with hadronic decays of $W$ and $Z$ bosons in association with large missing transverse momentum (mono-$W/Z$ searches) due to the larger dataset and further optimization of the event selection and signal region definitions. In addition to the mono-$W/Z$ search, the as yet unexplored hypothesis of a new vector boson $Z^\prime$ produced in association with dark matter is considered (mono-$Z^\prime$ search). No significant excess over the Standard Model prediction is observed. The results of the mono-$W/Z$ search are interpreted in terms of limits on invisible Higgs boson decays into dark matter particles, constraints on the parameter space of the simplified vector-mediator model and generic upper limits on the visible cross sections for $W/Z$+DM production. The results of the mono-$Z^\prime$ search are shown in the framework of several simplified-model scenarios involving DM production in association with the $Z^\prime$ boson.