Search for Resonant Production of Dark Quarks in the Dijet Final State with the ATLAS Detector

In these proceedings, a search for a new $Z^\prime$ resonance decaying into a pair of dark quarks is presented. These dark quarks hadronise into dark hadrons before promptly decaying back as Standard Model particles. This analysis is based on proton-proton collision data recorded at $\sqrt{s}=13$ TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb$^{-1}$. After selecting events containing large-radius jets with high track multiplicity, the invariant mass distribution of the two highest-transverse-momentum jets is scanned to look for excess above a data-driven estimate of the Standard Model multijet background from QCD processes. No significant excess of events is observed and the results are thus used to set 95\% confidence-level upper limits on the production cross-section times branching ratio of the $Z^\prime$ to dark quarks as a function of the $Z^\prime$ mass for various dark-quark scenarios.