Hidden valley/dark sector searches

The quest to unravel the nature of dark matter remains one of the central challenges in particle physics. Recent results from the CMS and ATLAS experiments at the CERN LHC provide compelling insights across a wide spectrum of dark-sector scenarios, including searches for long-lived particles, dark photons, axion-like particles, and invisible decays of the Higgs boson. Highlights include novel approaches leveraging machine learning, advanced trigger systems, and displaced vertex techniques to probe long-lived particles with unconventional signatures. Stringent constraints are placed on dark-sector models such as the twin Higgs model, hidden Abelian Higgs, Supersymmetry, and strongly coupled dark QCD, with limits set on mediator masses up to about 5 TeV and dark photon decay lengths extending to 50 meters. Searches also target semi-visible jets, dark mesons, and dark Higgs bosons, placing exclusions in previously unexplored parameter spaces. This talk highlights the robust progress made in probing dark matter, and emphasizes the vital role of the LHC in exploring physics beyond the Standard Model.