Beschreibung:
Abstract: Supersymmetric models are a well motivated extensions of the Standard Model of Particle Physics able to solve problems with the Standard Model, such as the hierarchy problem, and can give a dark matter candidate. The supersymmetric partner to the top-quark, the top-squark, gives radiative corrections to the Higgs boson mass motivating a top-squark mass close to the electroweak scale.<br><br>Here, a search for top-squark pair-production in final states with one lepton with ATLAS data at a centre-of-mass energy of 13 TeV is presented. The mass of the top-squark is assumed to be close to the sum of the masses of the lightest neutralino and the top-quark. With an integrated luminosity of 139 fb⁻¹ no significant excess above the Standard Model expectation was found, hence the result was interpreted as exclusion limits on the top-squark and neutralino masses.<br><br>To enable searches such as the one performed, as well as precisions measurements, a good understanding of the detector is paramount. One crucial part in the reconstruction of tracks of charged particles is the knowledge of the exact position of the different tracking detector modules. These positions are determined in the detector alignment. Here, the determination of biases on track parameters remaining after the alignment is presented. A novel method for the determination of distortions of silicon pixel sensors with collision data and the correction of these distortions is presented as well