A Data-Driven Method for Measuring Position Resolution in the DEAP-3600 DarkMatter Detector

Abstract

DEAP-3600 is a single-phase liquid Argon dark matter detector operated at SNOLAB in Ontario, Canada, searching for Weakly Interacting Massive Particles (WIMPs). It is well-established that astronomical and cosmological observations suggest the existence of some form of unseen matter in the universe, with the WIMP as one of the primary candidates. DEAP-3600 has set the leading limit on the WIMP-nucleon spin-independent cross-section for Argon based experiments, at 3.9 × 10−45 cm2 (1.5 × 10−44 cm2) for a 100 GeV c−2 (1 TeV c−2) mass WIMP (90% C.L.). A key factor in mitigating one source of backgrounds is the removal of events caused by contaminants on the inner surface of the acrylic vessel, achieved through means of position reconstruction and a fiducial cut on the reconstructed spherical radius. Understanding the precision of the reconstruction is therefore vital to knowing its effectiveness and so the goal of this project was to develop a method of measuring the position resolution in data. Using a process of event splitting this goal was achieved, demonstrating resolutions between 30 and 45 mm at the fiduciary boundary and at the energy range considered for candidate WIMP events.