MODERN DETECTORS TO STUDY THE STANDARD MODEL AND BEYOND
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The needs for experimental proof of physics beyond the Standard Model (SM) andthe Dark Matter theories leads us to develop new detectors for high energy and highluminosity experiments. In this context, ATLAS with the muon upgrade (New SmallWheel project in particular) is an example of new detector technology designed for theHigh Luminosity LHC (HL-LHC). A big challenge is imposed on the conventional gaseousdetectors used for muon tracking and triggering. The high rate environment conditionsprevailing in HL-LHC will push the detectors to ful ll stringent requirements in terms oftime and spatial resolution.A search for Dark Matter experiment, called NA64 and located in one of the exit linesfrom the Super Proton Synchrotron (SPS) facilities at CERN, provides another exampleof the need for a new generation of detectors. The NA64 is looking speci cally for DarkMatter on invisible or visible decays of dark photons. Such detection requires a delicateunderstanding of every single event and a highly pure electron beam.For these two experiments, a team from the Physics Department of the UniversidadSanta Maria (USM) has built two detectors; a small-Strip Thin Gap Chamber (sTGC)and a compact calorimeter with fast scintillator crystals LYSO.In this dissertation, we rst present the novel gaseous detector sTGC and the constructionmethod. A gain uniformity measurement is shown as well as its stability under ahigh rate environment condition. These two tests are presented as a quality control afterthe sTGC Module 0 is built. Two beam tests are carried out to study spatial resolutionof the 3:2mm strips and pad timing performance. Both are new features to provide fasttrigger for the Region of Interest.In the second part, we focus on spectroscopy studies on the new Gamma IrradiationFacility (GIF++) at CERN. A method of peak identi cation using Wavelets is shownas well as fast algorithm to reconstruct pile-up events. Spectra of dierent attenuation lters from GIF++ are shown with estimated attenuation factors.In the last chapter, we present a particle identi cation technique as a solution to thebeam contamination in the NA64 experiment. A brief explanation of the dark photonmeasurements is shown. Afterwards we show results of hadron suppression level fromdierent detectors using synchrotron radiation as particle identi cation technique. Lastlywe show the rst measurements of dark photon invisible decays where no dark photonstrahlunginteraction is found so far with 109 events on target.