Search for scalar top quark pair production in natural gauge mediated supersymmetry models with the ATLAS detector in pp collisions at √s = 7 TeV

The results of a search for pair production of the lighter scalar partners of top quarks (i˜1) in 2.05 fb−1 of pp collisions at √s = 7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (e,μ) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are interpreted in the framework of R-parity conserving, gauge mediated Supersymmetry breaking ‘natural’ scenarios, where the neutralino (χ˜1/0) is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for 115 GeV<mχ˜1/0<230 GeV at 95% confidence level, reaching an exclusion of mi1˜<330 GeV for mχ˜10=190 GeV. Scalar top quark masses below 240 GeV are excluded for all values of mχ˜1/0>mZ.