WIDG Seminar: Carl Rethmeier, Carleton University: “Measurement of Alpha-Decaying Backgrounds and the Search for 5.5 MeV Solar Axions in DEAP-3600”

Event time: 
Tuesday, October 13, 2020 - 12:00pm to 1:00pm
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Event description: 

DEAP-3600 is a liquid argon (LAr) based spin-independent direct dark matter search experiment. It is designed to detect nuclear recoils induced by the elastic scattering of weakly interacting massive particles (WIMPs) on argon nuclei. Last year, DEAP-3600 reported its second physics result that included the best reported upper limit on the WIMP-nucleon spin-independent cross section on a LAr target of 3.9×10^−45 cm^2 for a 100 GeV/c^2 WIMP mass at 90% C. L. An essential component of this result involved measuring the rates of alpha-decays within the detector and determining their impact on the expected background rate in the WIMP search region. The techniques used to measure and characterize these rates in-situ are presented. In addition, DEAP-3600’s large target mass and excellent ability to distinguish between electronic and nuclear recoils makes it well-suited for the detection of 5.5 MeV solar axions, which would produce electronic recoils in the LAr, at higher energy than most backgrounds. In this talk I will discuss the various components of the 5.5 MeV solar axion search analysis, including the calibration of the energy response function on AmBe neutron calibration data, development of the Monte Carlo based background and signal models, the algorithm developed to fit the MC model to the data, and the approach that will be used to calculate the final result.