Search for dark photon dark matter: Dark <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>E</mml:mi></mml:math> field radio pilot experiment
Benjamin Godfrey, J. A. Tyson, Seth Hillbrand, J. Balajthy, Daniel Polin, S. M. Tripathi, Shelby Klomp, Joseph Levine, Nate MacFadden, Brian H. Kolner, M. Smith, Paul Stucky, A. Phipps, Peter W. Graham, K. D. Irwin
Abstract
We are building an experiment to search for dark matter in the form of dark photons in the nano- to milli-eV mass range. This experiment is the electromagnetic dual of magnetic detector dark radio experiments. It is also a frequency-time dual experiment in two ways: We search for a high-Q signal in wide-band data rather than tuning a high-$Q$ resonator, and we measure electric rather than magnetic fields. In this paper we describe a pilot experiment using room temperature electronics which demonstrates feasibility and sets useful limits to the kinetic coupling $\ensuremath{\epsilon}\ensuremath{\sim}{10}^{\ensuremath{-}12}$ over 50--300 MHz. With a factor of 2000 increase in real-time spectral coverage, and lower system noise temperature, it will soon be possible to search a wide range of masses at 100 times this sensitivity. We describe the planned experiment in two phases: Phase-I will implement a wide band, 5-million channel, real-time FFT processor over the 30--300 MHz range with a back-end time-domain optimal filter to search for the predicted $Q\ensuremath{\sim}{10}^{6}$ line using low-noise amplifiers. We have completed spot frequency calibrations using a biconical dipole antenna in a shielded room that extrapolate to a $5\ensuremath{\sigma}$ limit of $\ensuremath{\epsilon}\ensuremath{\sim}{10}^{\ensuremath{-}13}$ for the coupling from the dark field, per month of integration. Phase-II will extend the search to 20 GHz using cryogenic preamplifiers and new antennas.