Impact of LHC Searches on NLSP Top Squark and Gluino Mass

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We explore the implications of 7 TeV LHC searches for a scenario in which one of the stops is the next-to lightest supersymmetric particle (NLSP). The NLSP stop (t₁) is assumed to decay exclusively into neutralino and charm quark. We consider processes where the stops are pair produced together with a hard QCD jet. We also consider stop quarks from gluino decays, g→ tt₁+tt₁. We show that the monojet ATLAS and CMS searches corresponding to 1 fb⁻¹ of integrated luminosity are sensitive to stop masses of up to 160 GeV, with the 20% neutralino-stop coannihilation region essentially ruled out for Mt₁ 140 GeV. The region Mt₁ 130 GeV is excluded with even relatively larger mass difference, Mt₁-Mχ₁⁰ 40 GeV, by the multi-jets search. The b-jet and same-sign dilepton searches are sensitive to a heavier gluino because they only pick up gluino pair production events followed by top quarks decaying into b-jets and same-sign dileptons, respectively. We find that the LHC data places a lower limit on the gluino mass in this scenario of about 600 GeV (700 GeV) from b-jets (same-sign dileptons) searches.