Searches for supersymmetry with two same-sign or at least three leptons with the ATLAS experiment

Two searches for supersymmetry (SUSY) in events with two leptons of the same electric charge or at least three leptons are presented. The first search targets the pair production of electroweak gauginos and the second one targets the pair production of strongly-interacting squarks and gluinos. The analyses use 139 fb−1 of proton-proton collisions data collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. No significant excesses over the Standard Model (SM) predictions are observed. The results are interpreted in the context of different R-parity conserving and R-parity violating scenarios. Exclusion limits at 95% CL are set on the masses of the superpartners involved in the considered scenarios. Model-independent upper limits on the BSM events that may contribute to the signal regions defined in the analyses are also computed.