Search for Direct Pair Production of Top Squark in the Final State of Two Tau Leptons at ATLAS

The first hadron collider search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino is performed using data from proton--proton collision at the Large Hadron Collider. The collision data collected by the ATLAS detector corresponding to an integrated luminosity of 20 fb$^{-1}$ at the center-of-mass energy of 8 TeV are used for these results. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is observed. Exclusion limits at $95\%$ confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the 87 GeV LEP limit to the top squark mass, lower limits between 490 GeV and 650 GeV are placed on the top squark mass within the model considered.