Many types of astronomical observations show decisively that most of the mass in the Universe is of an unknown form, unlike ordinary matter. This "dark matter" fills the universe and clumps over cosmic time under its own gravitational self attraction. Our current understanding of physics cannot explain dark matter; its existence is evidence for new physics! Its physical nature is a central unanswered question in science. Sensitive searches for weakly interacting massive particles in the GeV range have found nothing. Other possibilities for dark matter, such as the ultra-low mass nano eV to milli eV regime remain unexplored. A natural candidate for vector dark matter is the hidden photon, which can couple to electromagnetism. A group at UC Davis led by Tony Tyson are working on an extremely sensitive laboratory experiment: "Dark E-field Radio" which leverages cryogenic microwave detectors and FPGA technology in a GHz wide real-time spectral analysis. The result will be a 10,000-fold improvement over current astrophysical limits in dark matter detection searches in this vast unexplored ultra-low mass regime. To date, they have carried out a pilot experiment which has demonstrated feasibility. The research is supported by the DOE, the Brinson Foundation, and the Nokia Foundation.
The UC Davis group recently published a paper, let by grad student Ben Godfrey: http://arxiv.org/abs/2101.02805
Projected reach of the Dark E-Field Radio experiment at UC Davis. The weak kinetic mixing factor is plotted vs dark photon mass. Regions excluded by astrophysics are shown. Planned ADMX axion and hodoscope searches are shown in yellow. The orange points show calibrated exclusion regions at 4 spot frequencies at 5 sigma measured using the current pilot experiment. The red dot shows the point exclusion limit measured by Phipps et al. (2019). Phase-1 shows extrapolated limits using current setup after 1-year of real-time data acquisition. Phase-2 are cryogenic experiments covering the entire range 10 MHz -- 20 GHz, ultimately to THz.