Constraining low fine tuned supersymmetric models with simplified models spectra results based on CMS and ATLAS searches

Abstract

The ATLAS and CMS collaborations at the Large Hadron Collider (LHC) have performed a wide range of searches for physics beyond the standard model (BSM), during their run 1 at \Unit{8}{TeV}. Many of these searches target supersymmetric signatures. In order to ease the interpretation of these results, simplified models have been introduced recently. They provide a context in which the experimental results are interpreted as upper limits on production cross sections, introducing only a limited set of new BSM particles. Given a full theoretical model, it is nevertheless still a non-trivial task to decide, whether any of these simplified models results exclude the theory or not. A software framework called \smodels has been developed recently. It decomposes a given $\mathbb{Z}_2$-symmetric BSM model into its simplified models spectra (SMS) topologies and matches them with a database of the experimental simplified models results. The database that contains the experimental upper limits was maintained and improved within the scope of this thesis. A software tool to access the database as conveniently as possible was developed and constantly enhanced. This tool was used to validate the framework and restructure the database. The latest official version of the software tool, \smodelsv was applied to a scan over a parameter space determined by a low fine tuned (LFT) scenario. This scenario is a subset of the 19-parameter phenomenological minimal supersymmetric model (pMSSM). The motivation behind this region of parameter space is the question of ``naturalness'' within the pMSSM, i.e. how the mass of the newly found Higgs boson is stabilized at the electroweak scale. Another instance is to understand, if the concept of naturalness is compatible with the fact, that no experimental evidence for the existence of supersymmetry has been found so far. The scan is analysed and interpreted in this thesis. The mass spectrum in this LFT scenario is found to have very light top and bottom squarks often accompanied by light electro weak sparticles, allowing rather complex decay patterns. Amongst others this results in several interesting SMS topologies, for which no applicable simplified model results are available by now. Those topologies are understood in terms of supersymmetric decay chains. Regions of parameter space, which still remain unchallenged by current SUSY searches at the LHC are provided. Interesting new topologies for future SMS interpretation of data collected by the ATLAS and the CMS collaborations are proposed.