Search for pair production of top squarks and for dark matter in final states with two leptons using data collected by the ATLAS experiment during the LHC Run 2

A search for the direct pair production of top squarks $(\tilde{t})$ and for dark matter in events with two opposite-charge leptons, jets and missing transverse momentum is presented. The analysis is based on 139 fb$^{-1}$ of proton-proton collision data recorded by the ATLAS experiment at the Large Hadron Collider (LHC) at $\sqrt{s} = 13$TeV. Concerning the pair production of top squarks, current results extend previous exclusion limits with sensitivity across a wide range of mass differences between the $\tilde{t}$ and the lightest neutralino $\tilde{\chi}^0_1$. Furthermore, spin-0 mediator dark matter models are considered, with the mediator being produced in association with a pair of top squarks. No significant deviations from the Standard Model expectations are observed and limits at 95%confidence level (CL) are set on the masses of $\tilde{t}$, $\tilde{\chi}^0_1$ and dark matter mediators.