Position reconstruction using photon timing for the DEAP-3600 dark matter experiment

Abstract: DEAP-3600 is a single-phase liquid argon dark matter detector being operated 2 km underground at SNOLAB, Sudbury, Canada. The detector consists of 3.3 tonnes of ultra-pure liquid argon in a spherical acrylic cryostat instrumented with 255 photomultiplier tubes. Natural radioactive contamination in the acrylic vessel or TPB wavelength shifter can alpha-decay. Reconstruction of the position of the interactions taking place in the detector uses information about the number of photoelectrons detected in each PMT and when they were detected. Including this information in our suite of cuts allows us to identify and remove almost all surface background events. A method of event position reconstruction emphasizing photon timing is presented here.