ADMX-Orpheus First Search for 70 $\mu$eV Dark Photon Dark Matter: Detailed Design, Operations, and Analysis

TL;DR

This paper reports on the first search for dark photon dark matter using the ADMX-Orpheus experiment, which employs a novel dielectric-loaded cavity to explore higher mass ranges with improved detection volume.

Contribution

It introduces a new cavity design for dark matter detection that extends the search to higher frequencies and masses, enhancing the sensitivity of haloscope experiments.

Findings

No dark photon signal detected in the 65.5 to 69.3 μeV range.

Demonstrated the effectiveness of dielectric-loaded cavities for high-mass dark matter searches.

Provided a framework for future axion and dark photon exploration.

Abstract

Dark matter makes up 85% of the matter in the universe and 27% of its energy density, but we do not know what comprises dark matter. It is possible that dark matter may be composed of either axions or dark photons, both of which can be detected using an ultra-sensitive microwave cavity known as a haloscope. The haloscope employed by ADMX consists of a cylindrical cavity operating at the TM$_{010}$ mode and is sensitive to the QCD axion with masses of few $\mu$eV. However, this haloscope design becomes challenging to implement for higher masses. This is because higher masses require smaller-diameter cavities, consequently reducing the detection volume which diminishes the detected signal power. ADMX-Orpheus mitigates this issue by operating a tunable, dielectrically-loaded cavity at a higher-order mode, allowing the detection volume to remain large. This paper describes the design, operation, analysis, and results of the inaugural ADMX-Orpheus dark photon search between 65.5 $\mu$eV (15.8 GHz) and 69.3 $\mu$eV (16.8 GHz), as well as future directions for axion searches and for exploring more parameter space.