Abstract

Dark Matter (DM) constitutes a substantial but unexplained fraction of the universe, and the Standard Model (SM) of particle physics offers no viable candidate, highlighting the need for new theories and detection strategies. Numerous theoretical models predict DM particles, making their detection a strong pillar of the Large Hadron Collider (LHC) physics program. Yet, no direct evidence has been found so far. The lack of discovery indicates that if DM lies within the LHC ’s reach, its experimental signature may be subtle. New theories suggest DM isn’t just one particle, but part of a hidden dark sector (DS). This DS is governed by a new dark force binding DM in a way that mirrors the SM, described by the dark Quantum Chromodynamics (dark QCD ) framework. This dark force mediates interactions within the DS and between DS and SM particles. Dark QCD models predict fundamental components, i.e. dark quarks, confined at an energy scale comparable to that of QCD , which hadronise to form dark hadrons decaying within the detector. Depending on their lifetimes, these dark hadrons can produce unique collider signatures like prompt semi-visible jets or displaced emerging jets. With new particle reconstruction techniques, experiments like ATLAS and CMS are finally starting to probe this hidden sector and the unconventional signatures that come along with it. Early experimental results are emerging, and we’re only at the beginning. In this talk, I’ll start with an overview of the ATLAS dark sector paradigm and then explore in detail what we’re searching for, how we’re going after it, and the kinds of unconventional signals that might appear in the detector.