R&D toward SuperCDMS at SNOLAB

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Observations of galaxies, superclusters, distant supernovae, and the cosmic microwave background radiation tell us that ~85% of the matter in the universe is not made of known particles. Deciphering the nature of this dark matter is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. A leading hypothesis is that it is comprised of Weakly Interacting Massive Particles, or WIMPs, that were produced moments after the Big Bang. If WIMPs are the dark matter, then their presence in our galaxy may be detectable via scattering from atomic nuclei in detectors located deep underground.The Cryogenic Dark Matter Search (CDMS) Collaboration has pioneered the use of low temperature phonon-mediated detectors to detect the rare scattering of WIMPs on nuclei and distinguish them from backgrounds. CDMS is currently operating at Soudan, Minnesota with 10 kg of iZIP detectors, which have already demonstrated a background rejection factor sufficient for zero background operation with several hundred kilogram targets. In order to fully use this capability, it is necessary to build a new larger and cleaner experimental set up and locate it at a much deeper site than Soudan to eliminate the cosmogenic neutron background. The baseline design of this new experiment (SuperCDMS SNOLAB) calls for a 100 kg germanium experiment located at SNOLAB, Sudbury, Canada adapting the iZIP technology to 100 mm diameter detectors of 1.4 kg mass each.This award provides support for Research and Development towards this experiment. It focuses on critical R&D goals: the testing and characterization of the proposed detectors, contribution to the design and testing of the cold hardware and electronics (novel HEMT and SQUID for ionization and phonon readout), and the procurement and characterization of the germanium crystals. Broader impacts: The SuperCDMS experiment will have a broad impact which extends beyond the dark matter search. The technical development will further advance phonon-mediated detectors, which have already found many applications in cosmology, astronomy and industry. The project will contribute to the training of undergraduate and graduate students and postdoctoral researchers, using techniques at the leading edge of measurement technologies. SuperCDMS scientists will continue their involvement in K-12, their collaboration with teachers and their support for promising high school students from underserved backgrounds.