Search

We report new limits on the kinetic mixing strength of the dark photon spanning the mass range 0.21 -- 1.24 $\mu$eV corresponding to a frequency span of 50 -- 300 MHz. The Dark E-Field Radio experiment is a wide-band search for dark photon dark matter. In this paper we detail changes in calibration and upgrades since our proof-of-concept pilot run. Our detector employs a wide bandwidth E-field antenna moved to multiple positions in a shielded room, a low noise amplifier, wideband ADC, followed by a $2^{24}$-point FFT. An optimal filter searches for signals with Q $\approx10^6$. In nine days of integration, this system is capable of detecting dark photon signals corresponding to $\epsilon$ several orders of magnitude lower than previous limits. We find a 95% exclusion limit on $\epsilon$ over this mass range between $6\times 10^{-15}$ and $6\times 10^{-13}$, tracking the complex resonant mode structure in the shielded room., Comment: 15 pages, 12 figures, submitted to PRD

How much do financial management fees cost investors? This article studies an approximate formula for the cumulative costs of annual Assets Under Management (AUM) fees. The formula states that an investment paying an annual fee of $\epsilon$% of AUM over $N$ years loses almost $N\epsilon$% of its value, compared to an investment with the same returns paying no fee. The article explains this formula intuitively, derives it analytically, and studies its approximation error. The article concludes with a discussion of the formula's uses and limitations., Comment: Updated acknowledgements

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 $\epsilon \sim 10^{-12}$ 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 $Q\sim 10^6$ line using low-noise amplifiers. We have completed spot frequency calibrations using a biconical dipole antenna in a shielded room that extrapolate to a $5 \sigma$ limit of $\epsilon\sim 10^{-13}$ 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., Comment: 11 pages, 13 figures. Updated to published version. Corrected minor error in Fig 12 x-axis; results unchanged