Search for direct scalar top pair production in final states with two tau leptons in pp collisions at √s = 8 TeV with the ATLAS detector

A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb−1 of proton–proton collision data at √s = 8 TeV. The data were collected by the ATLAS experiment at the LHC in 2012. Scalar top 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 found. Exclusion limits at 95% confidence level are set as a function of the scalar top and scalar tau masses. Depending on the scalar tau mass, ranging from the 87 GeV LEP limit to the scalar top mass, lower limits between 490 GeV and 650 GeV are placed on the scalar top mass.