The particle nature of dark matter is being investigated vigorously by searches for its production, annihilation, decay, and scattering. Assuming dark matter is produced thermally, dark matter particle masses must lie within a wide range of masses between the keV and TeV scales. Theoretical simplicity and the available technology motivated most existing direct searches for dark matter scattering to focus on masses above 10 GeV. As the parameter space for weak-scale dark matter diminishes, searches for low-mass dark matter are becoming increasingly important. New, well motivated dark matter models, such as asymmetric dark matter, predict such low-mass particles.
The Cryogenic Dark Matter Search Low Ionization Threshold Experiment
(CDMSlite) modified the operation and readout of existing SuperCDMS detectors. These detectors measure the dramatically enhanced signal from Luke-Neganov phonons that are generated as electrons and holes drift across a germanium crystal biased to 70 V. Thus, very small ionization signals produced by low-mass dark matter scattering become detectable. The latest world-leading results from CDMSlite will be presented.
Engineering and planning are underway for the new SuperCDMS SNOLAB experiment using silicon and germanium detectors optimized for Luke-Neganov operation (SuperCDMS HV) in addition to detectors designed to measure ionization and phonons independently (SuperCDMS iZIP). The HV detectors will be sensitive to eV scale energy depositions created by dark matter particles lighter than 1 GeV. The status and goals of the SuperCDMS SNOLAB project will be presented, in anticipation of starting operation in 2020.