Abstract
Results of searches for supersymmetry via direct production of third-generation squarks and gluinos are reported. The analysis use 20.3 fb−1 of proton-proton collision data recorded by the ATLAS experiment and 19.5 fb−1 recorded by the CMS experiment at a centre-of-mass energy of s=8 TeV. Different signal regions based on monojet-like and c-tagged event selections optimize the sensitivity for direct top squark pair production with small mass differences between the hypothetical supersymmetric particles. In an complementary approach, the heavier top squark is searched for under the assumption that a Z boson is emitted in its decay to the lighter top squark. This strategy retains sensitivity for mass configurations where signals of direct production of the lighter top squark are hard to distinguish from the top quark pair production background. For the case of the gluino, a soft lepton analysis improves sensitivity for small mass differences between the gluino and the lightest neutralino. No significant excess above the Standard Model background expectation is observed in any of the analyses. The resulting limits significantly extend previous results at colliders.
Highlights
Supersymmetry (SUSY) is an extension of the standard model (SM) which proposes a super-partner for each SM particle [1, 2, 3, 4, 5, 6] in order to mitigate the virtual contributions of the SM particles to the self energy of the Higgs Boson by contributions with opposite sign [7, 8]
A similar argument holds for the gluino, because it contributes to the top squark self-energy
Recent searches at the LHC have excluded light top squarks up to 600 GeV [9, 10] and gluinos up to 1.3 TeV [11, 12], these results are often obtained under the assumption of a large mass difference to the lightest supersymmetric particle (LSP)
Summary
Supersymmetry (SUSY) is an extension of the standard model (SM) which proposes a super-partner for each SM particle [1, 2, 3, 4, 5, 6] in order to mitigate the virtual contributions of the SM particles to the self energy of the Higgs Boson by contributions with opposite sign [7, 8]. Any decay products of the SUSY particles will fall short of reconstruction thresholds Such compressed mass configurations have been proposed to reconcile measurements of the dark matter relic density with theoretical predictions of models with SUSY [15, 16] but limits on direct production from collider searches are considerably weaker. These models can still be tested by exploting a peculiar property of the strong interaction: The colliding partons of the primary hard interaction can radiate off a high energetic parton that hadronizes and is reconstructed as a jet which recoils against the heavy SUSY system in the transverse plane A complete list of the most current results can be found in Ref. [25] for the CMS experiment and in Ref. [26] for the ATLAS experiment
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