Scalar-Magnetometer Search for Ultralight Dark Photon Dark Matter with a Single-Site, Two-Sensor Array: A 6-Channel DTFT Likelihood Analysis with Scalar Optically Pumped Magnetometers

TL;DR

This study presents a novel laboratory method using a two-sensor scalar magnetometer array to search for ultralight dark photon dark matter, setting new limits on the kinetic-mixing parameter within a specific mass range.

Contribution

It introduces a six-channel DTFT likelihood analysis with a differential scalar magnetometer setup to improve sensitivity to dark photon signals in a laboratory setting.

Findings

Established the most stringent direct limits on the kinetic-mixing parameter to date.

Analyzed 10.5 hours of data with a new likelihood framework.

Complemented astrophysical bounds with laboratory measurements.

Abstract

We report on a laboratory search for ultralight dark photon dark matter using a single-site, two-sensor scalar magnetometer array. The experiment employs two scalar optically pumped magnetometers (OPMs) operated in a differential configuration to suppress common-mode noise and enhance sensitivity to spatially coherent dark photon fields. We analyze 10.5 hours of continuous data with a six-channel complex data vector evaluated at the three physical frequencies of the expected dark photon signal triplet. Assuming Gaussian noise, we develop a likelihood framework to set robust, frequency-resolved upper limits on the kinetic-mixing parameter $\varepsilon$, which governs the coupling between Standard Model photons and dark photons. Within the mass range $4\times10^{-15}\,\mathrm{eV} \leq m_{A'} \leq 3\times10^{-14}\,\mathrm{eV}$, we obtain the most stringent direct laboratory limits to date on $\varepsilon$, complementing existing astrophysical bounds including those inferred from observations of the Leo-T dwarf galaxy.