Innovative silicon pixel sensors for a 4D VErtex LOcator detector for the LHCb high luminosity upgrade

To fully exploit the instantaneous luminosity that LHC could provide at interaction point 8, where the LHCb experiment is located, a second experiment upgrade, called upgrade II, is planned to take place during Long Shutdown 4 in 2033. In order for the experiment to improve or at least maintain the current physics performances also in the high luminosity condition, several detectors will have to be upgraded or replaced and this is particularly true for the VErtex LOcator (VELO). In fact, dedicated simulations have shown a significant decrease of the vertices and tracks reconstruction efficiencies of the current VELO detector due to the increased pile-up of the the high luminosity condition. Moreover the harsher radiation environment will also provide a higher radiation damage to the detectors, much higher than the current VELO detector can withstand. The most promising solution to recover the tracking and vertices performances in the high luminosity condition is the development of a new 4D vertex detector capable to measure the time information of the tracks by using pixel sensors with an accurate spatial and time resolution for the particles detection. This set the stage for the development of innovative pixel sensors with unmatched time resolution of the order of tens picoseconds and featuring high radiation hardness. The TimeSPOT (Time and SPace real-time Operating Tracker) project has the aim to cope with these requirements by means of new 3D silicon pixels optimized for the measurement of particle timing. The work described in this thesis has been done in the context of this project and concerns the accurate characterizations of the innovative 3D trench silicon sensors, developed by the TimeSPOT collaboration, in terms of time resolution, detection efficiency and radiation hardness.