Search for light top squark pair production in final states with leptons and b-jets with the ATLAS detector in √s = 7 TeV proton–proton collisions

The results of a search for pair production of light top squarks are presented, using 4.7 fb−1 of √s = 7 TeV proton–proton collisions with the ATLAS detector at the Large Hadron Collider. This search targets top squarks with masses similar to, or lighter than, the top quark mass. Final states containing exclusively one or two leptons (e,mu), large missing transverse momentum, light flavour jets and b-jets are used to reconstruct the top squark pair system. Global mass scale variables are used to separate the signal from a large t¯t background. No excess over the Standard Model expectation is found. The results are interpreted in the framework of the minimal supersymmetric Standard Model, assuming the top squark decays exclusively to a chargino and a b-quark. Light top squarks with masses from 120 GeV up to the top mass are excluded for neutralino masses around 55 GeV.