Development Of Pixel Detectors For The Inner Tracker Upgrade Of The Atlas Experiment

Development of Pixel Detectors for the Inner Tracker Upgrade of the ATLAS Experiment

Development of Pixel Detector for ATLAS Inner Tracker(ITK) Upgrade at HL-LHC and Searching for the Standard Model Higgs Boson Decay Into B-quark Pair with ATLAS Experiment

ATLAS is one of the two main experiments at LHC with the purpose of investigating the microscopic properties of matter to address the most fundamental questions of particle physics. After the achievements of the first years of running, the potential reach for new discoveries and precise measurements at LHC is being extended by pushing further the energy and luminosity frontiers through three upgrades of the accelerator culminating in the High Luminosity LHC (HL-LHC). To fully profit from the increased luminosity, two main upgrades of the ATLAS inner detector are planned. The first upgrade was already completed at the beginning of 2015 with the insertion of the IBL, a fourth pixel layer located at just 3.2 cm from the beam line. In the second major upgrade, foreseen for 2024, the full inner detector will be replaced by a completely new inner tracker fully made of silicon devices to cope with the high particle density and the harsh radiation environment at the HL-LHC, which during its operational period will deliver 3000 fb-1, almost ten times the integrated luminosity of the full LHC program. This thesis addresses the study of new n+-in-p active edge pixel detectors by developing two novel doping profile analysis methods to study the radiation damage effects on the pixel detectors performance. These methods are the 3D sims imaging method and the TLM Method. TCAD simulation has been used to simulate the doping profiles, the electrical behavior and the radiation damage. Validating the simulation models with data have been done. Moreover, clean-room characterization, as well as testbeam measurement have been performed to test the different detector designs. In the second part of the thesis, I discuss the observation of the standard model Higgs boson bb decay mode using the data collected by ATLAS during the LHC Run2 at center-of-mass energy 13 TeV and an integrated luminosity 79.8 fb−1 of a proton-proton collision. I contributed specifically to the search of the standard model Higgs boson in VH(bb) production mode. In the VH(bb) analysis we don't have any channel that considers the tau leptons in the final state. I have performed a feasibility study to verify the gain of using the taus in the analysis. In addition, for the VH(bb) analysis I have worked on the multi-jet background estimation in the 1-lepton channel using the dijet-mass analysis method.

Development of a New Tracker for the CMS Upgrade Phase 2 and Study of the HL-LHC Physics Reach

The standard model of particle physics provides a coherent description of highenergy physics processes and has been hugely successful in providing experimental predictions. Among its long list of achievements, the most significant is arguably that of the discovery of the Higgs boson half a century after being theorised, providing the last cornerstone needed for the standard model to become fully consistent. Despite huge successes, the standard model still suffers from major shortcomings. On the path leading towards a better understanding of particle physics, an in-depth study of the Higgs boson is key. This relentless work of characterising the properties of the Higgs boson is currently being undertaken at the Large Hadron Collider, where high-energy proton collisions are being recorded by dedicated detectors, providing a continuous improvement to the understanding of the standard model. Amid tremendous achievements, some processes, remain too weak to be detected with the current installations. One such measurement is the combined production of two Higgs bosons allowing for a direct handle on the Higgs self-coupling parameter of the standard model. To maximise the physics reach of the collider, it will be subjected to a major upgrade, allowing for a strong increase in luminosity. Such a dramatic change will bring major challenges to the experiments recording these collisions and upgrades are required if they are to maintain their outstanding performance. This thesis explores the upgrade of the CMS silicon strip detector, centred around the in-beam characterisation of detector module prototypes and discusses the physics reach of the upgraded machine, with an emphasis on Higgs boson pair production in the bbWW(l) final state.