Abstract
This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton–proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 {mathrm{fb}^{-1}} of collisions at a centre-of-mass energy of sqrt{s} = 8 TeV, although in some case an additional 4.7 {mathrm{fb}^{-1}} of collision data at sqrt{s}= 7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models.
Highlights
= 8 TeV, collision √in data at s some case an = 7 TeV are used
The analyses considered are those previously published by the ATLAS collaboration on the topic, together with new ones designed to increase the sensitivity to scenarios not optimally covered so far
The paper is organised as follows: Sect. 2 briefly reviews the expected phenomenology of third-generation squark production and decay; Sect. 3 reviews the general analysis approach followed by the ATLAS collaboration for SUSY searches; Sects. 4 and 5 present the exclusion limits obtained in specific models by combining the results of several analyses
Summary
The cross section proton collisions aftor√dsire=ct8stToepVpaaisr production a function in of proton– the stop mass as calculated with PROSPINO [43,44] is shown in. Several possible scenarios have been considered, the most common ones being the gaugeuniversality inspired mχ1± = 2mχ , favoured, for example, in mSUGRA/CMSSM models [51,52,53,54,55,56]; other interpretations include the case of a chargino almost degenerate with the neutralino, a chargino almost degenerate with the squark, or a chargino of fixed mass Another possible decay channel considered for the sbottom is b1 → bχ20 → bhχ (Fig. 2h), which occurs in scenarios with a large higgsino component of the two lightest neutralinos. Three different sets of pMSSM models are considered, which take into account experimental constraints from LHC direct searches, satisfying the Higgs boson mass and dark-matter relic density constraints, or additional constraints arising from considerations of naturalness. The sensitivity to these models is discussed in Sect.
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