Search for a heavy top partner in final states with two leptons with the ATLAS detector

The results of a search for direct pair production of heavy top partners in 4.7~ifb of integrated luminosity from $pp$ collisions at $sqrt{s}=7$~TeV collected by the ATLAS detector at the LHC are reported. Heavy top partners decaying into a top quark and a neutral non-interacting particle are searched for in events with two leptons in the final state. No excess above the Standard Model expectation is observed. Limits are placed on a supersymmetric scalartop and on spin-1/2 top quark partner. A spin-1/2 top quark partner with mass lower than $483 GeV$ is excluded at 95% confidence level, for a neutral non-interacting particle lighter than $100 GeV$.