Collaborative Research: The SuperCDMS at SNOLAB Science Program

A crucial research area in particle astrophysics is the search to uncover the nature of dark matter. A compelling possibility is that it consists of a new type of elementary particle that interacts very weakly with normal matter. These dark matter particles would be gravitationally bound to our galaxy such that they may be directly detectable in a sufficiently sensitive terrestrial experiment. The National Science Foundation (NSF) and Department of Energy (DOE) have jointly chosen next-generation experiments to continue the direct detection search for dark matter. SuperCDMS SNOLAB is one of these experiments, specifically directed towards the search for dark matter with masses < 10 GeV/c2 119 . The experiment is being largely fabricated and installed by a jointly funded DOE-NSF project, hereafter referred to as the SuperCDMS SNOLAB construction project. The Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) are also funding SuperCDMS SNOLAB. The experiment will be located at SNOLAB in Ontario, Canada, the deepest underground laboratory in North America. The SuperCDMS experimental program is a multiple institution, multi-thrust effort of which this proposal is a critical component. The collaboration has conducted a series of experiments de signed to directly detect dark matter, using ultra-pure germanium (Ge) and silicon (Si) crystals instrumented with ionization and phonon sensors and operated at cryogenic temperatures. The first CDMS experiments at Stanford and Soudan provided leading sensitivity to high-mass WIMPs. Recently, we have shifted our focus to <10 GeV dark matter candidates, where our technology has unique advantages given the low energy thresholds enabled by our athermal phonon sensor technology and Luke-Neganov phonon amplification techniques. The SuperCDMS SNOLAB construction project has passed the third Critical Decision (CD-3) review process and is now fabricating and installing the experiment, thus working toward project completion (CD-4). SuperCDMS SNOLAB is currently in the early operations stage of its operations program. In this phase, data is being collected as part of a campaign of detector and subsystem testing, calibration of the detectors, and experiment installation and integration. During the second and third years of this proposal, the operations program will include cryogenic systems tests, detector commissioning and the first science run of the full detector payload. A separate proposal has been submitted to this solicitation, “The SuperCDMS at SNOLAB Operations Program,” to fund travel and M&S in support of the operations program, as well as the NSF personnel who manage opera tions activities. The activities in this science proposal are fully coordinated with the SuperCDMS SNOLAB construction project and operations program, and the SuperCDMS Collaboration. The success of the efforts described in this proposal on a timescale consistent with the official construction project and operations schedules relies on support of personnel from Northeastern University, Northwestern University, SMU, UC Berkeley, University of Colorado Denver and the University of Florida, as outlined in this proposal. The scope of the work outlined in this proposal includes: (1) producing early science results from data taken with single detectors and a single detector tower, (2) characterizing and minimizing environmental noise and charge leakage in HV detectors, (3) characterizing low energy backgrounds in HV detectors, (4) measuring the