New Limit on Dark Photon Kinetic Mixing in the 0.2-1.2 $\boldsymbol{\mu}$eV Mass Range From the Dark E-Field Radio Experiment

TL;DR

This paper presents new experimental limits on dark photon kinetic mixing in the 0.2-1.2 μeV mass range using a wide-band radio detection method, significantly improving sensitivity over previous constraints.

Contribution

The study introduces an upgraded wide-band dark photon detection experiment with enhanced calibration and analysis techniques, setting more stringent limits on kinetic mixing.

Findings

Established new exclusion limits on kinetic mixing parameter ε.

Achieved sensitivity several orders of magnitude better than prior experiments.

Demonstrated the effectiveness of wide-band radio detection for dark matter searches.

Abstract

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.