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

TL;DR

This paper reports a search for scalar top quark pairs in proton-proton collisions at 7 TeV using the ATLAS detector, setting new exclusion limits on their masses within specific supersymmetry models.

Contribution

It presents the first search for scalar top quarks in natural gauge mediated supersymmetry models at 7 TeV with the ATLAS detector, establishing new mass exclusion limits.

Findings

No excess over Standard Model expectations was observed.

Scalar top quark masses up to 310 GeV are excluded for certain neutralino masses.

Exclusion limits extend to scalar top quark masses of 330 GeV for specific neutralino masses.

Abstract

The results of a search for pair production of the lighter scalar partners of top quarks in 2.05 fb-1 of pp collisions at sqrt(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 (electrons or muons) 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 is the next-to-lightest supersymmetric particle. Scalar top quark masses up to 310 GeV are excluded for the lightest neutralino mass between 115 GeV and 230 GeV at 95% confidence level, reaching an exclusion of the scalar top quark mass of 330 GeV for the lightest neutralino mass of 190 GeV. Scalar top quark masses below 240 GeV are excluded for all values of the lightest neutralino mass above the Z boson mass.