The optical simulation model of the DarkSide-20k Veto detector

Abstract DarkSide-20k is a rare-event search experiment aimed at finding signals of dark matter particles. It dual-phase detector that registers ionisation and scintillation originating from the particles interacting with liquid argon medium. enclosed in single-phase neutron veto tank, equipped Gd-loaded panels for capturing neutrons. Since vetoing particle identification are carried out using light signal, it crucial to maximise yield. Light collection efficiency depends on optical properties particularly detector, which has photosensor coverage order per cent, reflectivity walls big impact. To quantify amount collected light, comprehensive Geant4 simulation performed, uses characterisation data. In this work, detailed description optics model will be discussed.