Light Yield Study for Liquid Argon Dark Matter Detectors

Abstract

Weakly Interacting Massive Particles (WIMPs) are a promising solution to the dark matter problem. The DarkSide experiment looks for a scintillation signal produced when WIMPs collide with a liquid argon atoms. Discrimination against background events depends critically on the light yield, defined as the number of photoelectrons detected per unit of recoil energy. The prototype detector DarkSide-10 measured a light yield of 9.142 photoelectrons/keV in 2012. It uses the wavelength shifter Tetraphenylbutadiene (TPB) to convert UV photons to the visible range for detection. In this thesis, we use a liquid argon detector of diameter 3.35 inches and height 1.5 inches with a different wavelength shifter, P-Terphenyl (PTP). A light yield of 9.82 photoelectrons/ keV was measured using the full-absorption peak of a gamma ray source.