Research and development of the High-Granularity Timing Detector (HGTD) for the ATLAS Detector as the preparation of the High-Luminosity LHC operation phase

ATLAS (A Toroidal LHC Apparatus) is the biggest experiment at the Large Hadron Collider (LHC) at CERN. It is a general-purpose experiment that took part in the discovery of the Higgs boson in 2012. Since from 2029, LHC will start the high-luminosity (HL) phase, which will drastically increase the amount of proton-proton collisions in a given amount of time, ATLAS will undergo a major upgrade to cope with the increased amount of data and especially the harsh pile-up environment, the soft interactions polluting the collisions of interest. In this scope, the High-Granularity Timing Detector (HGTD) is being designed to improve the ATLAS reconstruction abilities and discard pile-up tracks in the forward region by adding high-resolution time measurements (30 ps per track). An excellent time resolution of HGTD will be achieved by using the new semiconductor sensors technology, i.e. Low Gain Avalanche Detectors (LGAD). This thesis is dedicated to the research and development for HGTD on several topics including mechanical aspects, LGAD sensors performance studies, track reconstruction enhancement and software development.