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

The search for dark matter (DM) particles produced in association with a hadronically decaying vector boson is performed with 36.1 fb$^{-1}$ of $pp$ collision data at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. This analysis improves on the 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, yet unexplored hypothesis of a new vector boson $Z'$ produced in association with dark matter is considered (mono-$Z'$~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 the 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 the $W/Z$+DM production. The results of the mono-$Z'$ search are shown in the frame of several simplified-model scenarios involving the DM production in association with the $Z'$ boson.