Searches for Supersymmetry in Multilepton Final States with the ATLAS Detector

Two searches for supersymmetry in multilepton final states are presented using $pp$ collisions at $\sqrt{s} = 8~$TeV in the ATLAS detector. First, a search for electroweak production of charginos and neutralinos in the three-lepton plus missing transverse momentum channel is detailed with an emphasis on the fake-lepton background estimation technique. No significant excess above the Standard Model prediction is observed in the signal regions. Exclusion limits are thus placed on simplified models of $\tilde\chi^\pm_1\tilde\chi^0_2$ production and decays via intermediate sleptons, SM gauge bosons, and Higgs bosons. The results are also interpreted in terms of the phenomenological MSSM. Next, a search for $R$-parity violating and $R$-parity conserving supersymmetric scenarios in the four-lepton channel is presented. No significant excess is observed, so exclusion limits are placed on $R$-parity violating simplified models in which the lightest supersymmetric particle is the lightest neutralino, which promptly decays to leptons. Exclusion limits are also placed on $R$-parity conserving simplified models of $\tilde\chi^0_2\tilde\chi^0_3$ production.