Search for Supersymmetric Top-Quark Partners Using Support Vector Machines and Upgrade of the Hadron Calorimeter Front-End Readout Control System at CMS

In this thesis a search for direct pair production of supersymmetric top-quark partners aswell as work on the upgrade of the front-end readout controller of the Hadron Calorimeter(HCAL) of the Compact Muon Solenoid (CMS) experiment are presented.The most appealing extension of the Standard Model (SM) is supersymmetry (SUSY), relating the integer spin (bosons) and half-integer spin elementary particles (fermions). Supersymmetric top-quark partners (t) around and below the TeV energy scale offer a solution to thehierarchy problem. Furthermore, R-parity conserving SUSY models propose a cold dark matter candidate in the form of stable lightest supersymmetric particles, e.g. lightest neutralinos(χ0 ).The analysis performed in this thesis is a search for top-squark pair production in a final state consisting of a single isolated lepton, jets, among which at least one is tagged asbottom-quark jet, and large missing transverse energy at the CMS experiment at the CERNLarge Hadron Collider (LHC) with 8 TeV center-of-mass energy. A new Support Vector Machines (SVM) High-Energy Physics interface (SVM-HINT) software is introduced to classifysignal events originating from new physics processes and the SM background. SVM-HINTis enhanced with a novel statistical significance based optimization algorithm providing astate-of-the-art classification power. Monte Carlo simulations are used in the training and optimization procedure, and high signal purity search regions are determined in the search fortop-squark pair production. The background event yields in each search region are predictedusing a data-driven background estimation method. The results are interpreted within a simplified model assuming a branching ratio of 100% to t → t χ0 . No significant discrepancybetween the data and the SM predictions has been observed. Exclusion limits were derived toconstrain the mt and mχ0 of the investigated simplified model. The sensitivity of the previoussearches with the 8 TeV center-of-mass energy in the single lepton final states is extended tomt = 675 GeV and mχ0 = 225 GeV.The results of the present analysis once again verified the necessity to reach higher centerof-mass energies and luminosities at the LHC. Such an upgrade will increase the radiationexposure of the readout electronics. A reliable operation of the detector electronics underthese harsh conditions is absolutely crucial. Therefore, a new front-end readout control system has been integrated to the upgraded electronics infrastructure of the CMS HCAL, whichsimultaneously sets up and controls all front-end modules. Furthermore, it recovers diagnostic information and responses immediately in case of unexpected events. A firmware for thenext-generation Front-End-Control module helping to accomplish these tasks has been developed. Consistency and reliability of the control system is successfully tested in the test-standsand irradiation beam tests.