Constraining the Dark Sector with the Mono-jet signature with the ATLAS detector at the LHC

This work presents the reinterpretation of the search for final states with at least one energetic jet and missing transverse momentum in the context of dark sector models with long-lived neutral particles. Results are based on 139 fb−1 of data collected in pp collisions at √s= 13 TeV by the ATLAS experiment during Run-2 at LHC. Decays of the Standard Model Higgs boson and of a new neutral heavy scalar mediator into long-lived particles are investigated in different channels. The resulting constraints generally extend those from dedicated searches at large proper lifetimes.