Abstract
A search for Supersymmetry involving the pair production of gluinos decaying via third-generation squarks to the lightest neutralino is reported. It uses an LHC proton--proton dataset at a center-of-mass energy $\sqrt{s} = 13$ TeV with an integrated luminosity of 3.2 fb$^{-1}$ collected with the ATLAS detector in 2015. The signal is searched for in events containing several energetic jets, of which at least three must be identified as $b$-jets, large missing transverse momentum and, potentially, isolated electrons or muons. Large-radius jets with a high mass are also used to identify highly boosted top quarks. No excess is found above the predicted background. For neutralino masses below approximately 700 GeV, gluino masses of less than 1.78 TeV and 1.76 TeV are excluded at the 95% CL in simplified models of the pair production of gluinos decaying via sbottom and stop, respectively. These results significantly extend the exclusion limits obtained with the $\sqrt{s} = 8$ TeV dataset.
Highlights
Supersymmetry (SUSY) [1,2,3,4,5,6] is a generalization of space-time symmetries that predicts new bosonic partners to the fermions and new fermionic partners to the bosons of the Standard Model (SM)
For the gluino models with stop-mediated decays in which there is a large mass difference between the gluino and the lightest supersymmetric particle (LSP), large-R jets identified as originating from highly boosted top quarks are employed
The background is dominated by tt þ jets, which is normalized in dedicated control regions
Summary
Supersymmetry (SUSY) [1,2,3,4,5,6] is a generalization of space-time symmetries that predicts new bosonic partners to the fermions and new fermionic partners to the bosons of the Standard Model (SM). In this paper, pairproduced gluinos decaying via stop and sbottom quarks are searched for using events with high jet multiplicity, of which at least three must be identified as b jets, large EmT iss, and either zero leptons (referred to as the Gtt 0-lepton channel) or at least one identified charged lepton (referred to as the Gtt 1-lepton channel) For both the Gbb and Gtt models, several signal regions are designed to cover different ranges of gluino and χ~. That analysis searched for gluinos decaying via stop quarks in events with at least three b-tagged jets and either zero or at least one identified lepton and obtained the best ATLAS limits for the Gtt models with massless and moderately massive LSP [20]. Simpilaffiffir searches performed wpiffitffih the CMS experiment using s 1⁄4 8 TeV [25,26,27,28,29,30] and s 1⁄4 13 TeV data [31,32,33,34] have produced comparable results to ATLAS searches
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