The DEAP-3600 detector is a single phase direct detection search for particle dark matter. It comprises 3600 kgs of liquid argon, with a 1000 kg fiducialised target volume, surrounded by 255 photomultiplier tubes (PMTs). The detector components are described along with the dark matter interaction mechanism. A method for identifying and removing after- pulses in the PMT waveforms is described and its impact on discrimination variables is investigated. It is shown that the detector energy threshold can be lowered from 120 photoelectrons to 94 photoelectrons while keeping the 39Ar, the detector’s most prominent background, leakage rate below 0.2 events in three years of running. A preliminary analysis of the after-pulsing PDF and rate from in situ calibration data is presented. Finally, the latest projected dark matter sensitivity is derived with a cross-section of 5.6 × 10−47 cm2 at a WIMP mass of 100GeV/cm2. This sensitivity is derived in relation to the most prominent background, it assumes there is no increase in background rate due to the change in energy threshold. Finally, a likelihood approach to setting a WIMP-nucleus cross section limit, including known backgrounds, is outlined.
|23 Jun 2016
|Unpublished - 2016