Search for a heavy scalar at the LHC, and consolidation of service electronics and sensors of the CMS Inner Tracker for HL-LHC

This thesis tackles two topics belonging to the CMS experiment at LHC, with a part focused on the search of high mass resonances decaying into two W bosons using the data collected from 2016 to 2018 by CMS, and another part related to the HL-LHC tracker upgrade. It addresses different stages of the future CMS Inner Tracker (IT) , starting from the single sensor characterization to larger-scale system tests. The search is performed by reconstructing the two W bosons, one with a leptonic final state and the other one reconstructed from the hadronic decay. This final state enhances the sensitivity to high mass resonances, despite the complexity of the hadronic reconstruction. Vector Boson Fusion and Gluon Gluon Fusion production mechanisms are considered, and an interpretation with minimal theoretical constraint is depicted. The analysis features a novel Machine Learning technique based on an adversarial neural network to reduce the model dependency on the signal mass hypothesis considered. Partial unblinding results are presented, assessing the compatibility with the background-only hypothesis. In the High Luminosity CMS IT, silicon planar and 3D pixel detectors will be employed. The latter are obtained by etching the electrode inside the silicon bulk directly. Given the unprecedented level of irradiation damage foreseen during the HL-LHC phase, it is crucial to characterize the radiation tolerance of the silicon detectors that will equip the tracker. This thesis presents the results obtained with irradiated 3D silicon pixel detectors measured at the test beam facility. The results show that maximum hit efficiency and good spatial resolution can be obtained with such technology, despite the extreme level of irradiation. For this future tracker, the power will be distributed for the first time through a serial powering scheme; considering the novelty of the serial powering, complex systems are realized to asses its stability. In this work, the realization and the measurements of a system featuring 8 final-size modules powered in series, on the prototype mechanical structure and read-out with the final read-out chain are presented.