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

Abstract

The results of a search for pair production of the lighter scalar partners of top quarks (<math><msub is="true"><mrow is="true"><mover accent="true" is="true"><mi is="true">t</mi><mo is="true">˜</mo></mover></mrow><mrow is="true"><mn is="true">1</mn></mrow></msub></math>) in 2.05 fb−1 of pp collisions at <math><msqrt is="true"><mi is="true">s</mi></msqrt><mo is="true">=</mo><mn is="true">7</mn></math> 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 (<math><mi is="true">e</mi><mo is="true">,</mo><mi is="true">μ</mi></math>) 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 (<math><msubsup is="true"><mrow is="true"><mover accent="true" is="true"><mi is="true">χ</mi><mo is="true">˜</mo></mover></mrow><mrow is="true"><mn is="true">1</mn></mrow><mrow is="true"><mn is="true">0</mn></mrow></msubsup></math>) is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for <math><mn is="true">115</mn><mtext is="true"></mtext><mtext is="true">GeV</mtext><mo is="true">&lt;</mo><msub is="true"><mrow is="true"><mi is="true">m</mi></mrow><mrow is="true"><msubsup is="true"><mrow is="true"><mover accent="true" is="true"><mi is="true">χ</mi><mo is="true">˜</mo></mover></mrow><mrow is="true"><mn is="true">1</mn></mrow><mrow is="true"><mn is="true">0</mn></mrow></msubsup></mrow></msub><mo is="true">&lt;</mo><mn is="true">230</mn><mtext is="true"></mtext><mtext is="true">GeV</mtext></math> at 95% confidence level, reaching an exclusion of <math><msub is="true"><mrow is="true"><mi is="true">m</mi></mrow><mrow is="true"><msub is="true"><mrow is="true"><mover accent="true" is="true"><mi is="true">t</mi><mo is="true">˜</mo></mover></mrow><mrow is="true"><mn is="true">1</mn></mrow></msub></mrow></msub><mo is="true">&lt;</mo><mn is="true">330</mn><mtext is="true"></mtext><mtext is="true">GeV</mtext></math> for <math><msub is="true"><mrow is="true"><mi is="true">m</mi></mrow><mrow is="true"><msubsup is="true"><mrow is="true"><mover accent="true" is="true"><mi is="true">χ</mi><mo is="true">˜</mo></mover></mrow><mrow is="true"><mn is="true">1</mn></mrow><mrow is="true"><mn is="true">0</mn></mrow></msubsup></mrow></msub><mo is="true">=</mo><mn is="true">190</mn><mtext is="true"></mtext><mtext is="true">GeV</mtext></math>. Scalar top quark masses below 240 GeV are excluded for all values of <math><msub is="true"><mrow is="true"><mi is="true">m</mi></mrow><mrow is="true"><msubsup is="true"><mrow is="true"><mover accent="true" is="true"><mi is="true">χ</mi><mo is="true">˜</mo></mover></mrow><mrow is="true"><mn is="true">1</mn></mrow><mrow is="true"><mn is="true">0</mn></mrow></msubsup></mrow></msub><mo is="true">&gt;</mo><msub is="true"><mrow is="true"><mi is="true">m</mi></mrow><mrow is="true"><mi is="true">Z</mi></mrow></msub></math>.