Searches for direct scalar top pair production in final states with two leptons using the stransverse mass variable and a multivariate analysis technique in $\sqrt{s} = 8$ TeV pp collisions using 20.3 fb$^{-1}$ of ATLAS data

Two searches are presented for the direct pair production of supersymmetric partners of the top quark in 20.3 fb$^{-1}$ of $pp$ collisions at 8 TeV, collected by the ATLAS detector at the LHC. Top squarks are sought for in events with two leptons ($e$ or $\mu$) in the final state. No excess above the Standard Model expectation is observed. Exclusion limits at 95$\%$ confidence level are derived on the mass of the top squark assuming it decays with 100$\%$ branching ratio into a $b$-quark and a chargino, using a search which exploits the stransverse mass variable, or into a top quark and the lightest neutralino using a multivariate analysis technique.