Searches for Dark Matter in events with long-lived particles at the LHC

The ATLAS, CMS and LHCb collaborations searched for Dark Matter (DM) in events with long-lived particles. Many theories of physics beyond the Standard Model predict the existence of stable, neutral, weakly-interacting and massive particles that are putative Dark Matter candidates. The observation of such matter at a collider could only establish that it is neutral, weakly-interactive, massive and stable on the distance-scales of tens of meters. The searches are performed using the LHC Run-I and Run-II datasets recorded with the ATLAS, CMS and LHCb detectors in proton-proton collisions at a center-of-mass energy of 7, 8 and 13 TeV. Signatures include both long-lived particles produced in association with DM and long-lived DM particles (e.g. dark photons decay in lepton-jets). This presentation covers only some of the many researches carried out with the LHC experiments in recent years. No deviation from SM background expectation was found up to now and exclusion limits on DM production cross section were set.