Measurements of the Tau g-2 in Pb-Pb Collisions at the CMS Experiment and Future Improvements of the CMS Tracker

Abstract

Although the Standard Model (SM) of particle physics has been remarkably successful, it still faces some theoretical and experimental challenges, including an up to 5.1 sigma deviation of the observed g-2 factor of muons compared to the SM prediction, hinting on beyond SM contributions. Such contributions are expected to be larger for tau leptons due to their higher mass, but the short lifetime of tau leptons prohibits a direct measurement of its g-2 factor. In this dissertation, the first measurement of the tau g-2 factor at the LHC and an improved measurement both using the recorded ultraperipheral collisions of Pb ions by the CMS experiment during Run2 of the LHC are presented. The prospects of this measurement for Run3 and the HL-LHC era are discussed, which motivate the upgrade of the CMS detector and particularly the tracking system, for which my contributions are detailed.