A LIKELIHOOD RATIO ALGORITHM FOR REMOVING LOCALIZED ALPHA PARTICLE BACKGROUNDS IN THE DEAP-3600 DETECTOR

• Author / Creator

  Mielnichuk, Courtney T.

• DEAP-3600 (Dark Matter Experiment using Argon for Pulse shape discrimination) is a single phase dark matter experiment using a tonne-scale mass of liquid argon as a target to observe spin-independent interactions with Weakly Interacting Massive Particles (WIMPs). Alpha decays from radioactive nuclei accumulating on the surface of detector materials are a background concern for the experiment. Specifically, alpha decays occurring in the neck region of the detector produce signals with characteristics similar to those expected for WIMP interactions. In order to estimate the potential background from alpha decays in the detector neck, projected material radioactivity levels have been incorporated into Monte Carlo simulations. A likelihood ratio algorithm to discriminate between neck alpha decays and a WIMP signal has been developed based on Monte Carlo simulation. The benefit of implementing a likelihood ratio cut, both in comparison and in combination with a fiducial volume cut, has been studied. Preliminary results of the likelihood ratio applied to commissioning data are also studied.

• Subjects / Keywords

  • Alpha particle backgrounds
  • DEAP-3600
  • Likelihood ratio algorithm

• Graduation date

  Spring 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3BN9XF6T

• 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.