The ATLAS Experiment at the CERN Large Hadron Collider is a particle physics experiment to study fundamental particles and their interactions at very high energies. Supersymmetry is a theory of new physics beyond the Standard Model of particle physics. A search for directly produced pairs of the supersymmetric partner of the top quark was performed using 20 fb^-1 of proton--proton collision data at a centre of mass energy of 8 TeV taken in 2012. The search targeted a model where the supersymmetric partner of the top quark (``scalar top'') decays via the supersymmetric partner of the tau lepton (``scalar tau'') into the supersymmetric partner of the graviton (``gravitino''). Scalar top candidates were searched for in pp collision events with either two hadronically decaying taus, two light leptons (electrons or muons), or one hadronically decaying tau and one light lepton. The numbers of events passing the analysis selection criteria agree with the Standard Model expectations. Exclusion limits at the 95% confidence level were set as a function of the scalar top and scalar tau masses. Depending on the scalar tau mass, ranging from the 87 GeV limit set by the LEP experiments to a few GeV below the scalar top mass, lower limits between 490 GeV and 640 GeV were placed on the scalar top mass within the model considered.

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Results are presented from a search for the electroweak production of supersymmetric particles in pp collisions in final states with two tau leptons. The data sample corresponds to an integrated luminosity between 18.1 inverse femtobarns and 19.6 inverse femtobarns at sqrt(s) = 8 TeV, collected by the CMS experiment at the LHC. The observed event yields in the signal regions are consistent with the expected standard model backgrounds. The results are interpreted using simplified models describing the pair production and decays of charginos or tau sleptons. For chargino pair production, assuming that the third-generation sleptons are the lightest sleptons and that their masses lie midway between that of the chargino and the lightest neutralino, an excluded region in the plane of the neutralino mass vs. chargino mass is obtained. Chargino masses below 420 GeV are excluded at a 95% confidence level in the limit of a massless neutralino, and for neutralino masses up to 100 GeV, chargino masses up to 325 GeV are excluded at 95% confidence level. Constraints are also placed on the cross section for pair production of tau sleptons as a function of mass, assuming a massless neutralino.

A search for pair production of scalar top (stop) quarks has been performed in the lepton+jets channel in ̃1 fb-1 of data at the D0 experiment. Kinematic differences between $ar{t}$1$ ilde{t}$1 and the dominant t$ar{t}$ process are used to separate the two reactions. For stop-quark masses of 145-175 GeV, and chargino masses of 105-135 GeV, to which the stop quarks decay ($ ilde{t}$1 → $ ilde{X}$1+b), we obtain upper limits on the $ ilde{t}$1$ar{t}$1 cross section at 95% confidence, that are a factor of ̃7-12 larger than expected from the Minimal Supersymmetric Standard Model (MSSM), as calculated in a next-to-leading-order (NLO) approximation in quantum chromodynamics (QCD).