Optimization of the simulation framework in the Stereo Experiment to characterize the detector response and optical properties of the liquid scintillators

The Stereo experiment is one of the pioneering efforts to test the light sterile neutrino hypothesis at short baselines from nuclear reactors. Placed at $\sim$10m from the Institut-Laue-Langevin research reactor in Grenoble, France, Stereo is observing electron antineutrino signals since 2016. Given its cell-wise segmented volume, Stereo can perform spectral analyses at different baselines. This allows to test the compatibility of the observed flux with different oscillatory hypotheses, provided by a dedicated Monte Carlo simulation of the detector and the physics within. This thesis addresses the process of fine tuning performed on the simulation framework of Stereo. In particular, the production, transport and quenching of scintillation light in the detector has been adjusted to match calibration data, including the characterization of the light yield, attenuation length and fluor quantum yields of the liquid scintillator components. A new optical model for the separation walls has been implemented, successfully accounting for the increased light cross-talk between cells observed. Energy non-linearities in the response of the detector have also been investigated and reproduced in the simulation to the subpercent level. The process of tuning has lead to an excellent agreement of the reconstructed energy signal between calibration data and simulations, allowing Stereo to exclude a considerable portion of the allowed oscillation parameter space.