Search for the direct pair production of top squarks decaying to a b quark, a tau lepton, and weakly interacting particles, in $\sqrt{s} = 8 TeV$ pp collisions using $20 \; fb^{-1}$ of ATLAS data

Preliminary results of a search for direct pair production of supersymmetric partners of the top quark decaying via a $\tau$ slepton and with a gravitino in the final state ($ \tilde{t_1} \rightarrow b \nu_\tau \tilde{\tau_1} \rightarrow b \nu_\tau \tau \tilde G$) are reported. Top squarks are searched for in events with two leptons (electrons or muons) in the final state using $20.3 \; fb^{-1}$ of integrated luminosity from LHC $pp$ collisions at $\sqrt{s}$=8 TeV collected by the ATLAS detector. No excess above the Standard Model expectation is observed. Exclusion limits at 95$\%$ confidence level are placed as a function of the top squark and $\tau$ slepton masses. Models where the mass difference between the top squark and the $\tau$ slepton is below 35 GeV are excluded at 95$\%$ CL for top squark masses up to 480 GeV. Top squark masses below 170 GeV are excluded for all $\tau$ slepton mass values.