A Search for Dark Matter Interactions in the DEAP 3600 Detector Using Fiducial Masses Ranging from 1433 to 2966 kg

  • Author / Creator
    Farahani, Sina Safarabadi
  • The DEAP-3600 detector is a single-phase direct-detection Dark Matter (DM) experiment located 2 km underground at SNOLAB in Sudbury, Canada. The detector consists of 3279 kg of liquid Argon contained in a spherical acrylic vessel. DEAP-3600 was specifically designed to search for direct detection of dark matter candidates known as Weakly-Interacting Massive Particles (WIMPs).

    Radioisotope surface activity is a major source of background in dark matter experiments, and most experiments use a fiducial volume to remove these events, which reduces signal acceptance. The second result of DEAP-3600 published in 2019, used a fiducial radius of 630 mm reducing the detector volume by nearly 60%. Instead of only relying on position reconstruction algorithms and using a strict fiducial volume to
    remove surface background events, we designed a new veto algorithm to identify these events. This approach will enable us to tag and veto surface events and expand the fiducial volume up to 820 mm to increase signal acceptance and improve the limits we can set on the WIMP-nucleus cross-section. Using 386 live-days of physics data and a WIMP mass of 100 GeV/c^2, the 820 mm fiducial volume showed an improvement of the spin-independent WIMP-nucleon cross-section by more than 30% compared to a fiducial volume of 720 mm, an updated limit actively being considered by the DEAP-3600 collaboration. We set an upper limit on the WIMP-nucleon spin-independent cross-section of 3.8 × 10^{−45} cm^2 (1.4 × 10^{−44} cm^2) for a WIMP mass of 100 GeV/c^2 (1 TeV/c^2) at 90% confidence level.

  • Subjects / Keywords
  • Graduation date
    Fall 2023
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.