Completion of Phase I and Preparation for Phase II of the HAYSTAC Experiment

TL;DR

The paper reports on the completion of Phase I of the HAYSTAC experiment, which searches for dark matter axions using a microwave cavity, and outlines preparations and upgrades for Phase II to improve sensitivity and explore higher frequencies.

Contribution

It provides the first results from Phase I of HAYSTAC, including exclusion limits on axion models, and discusses planned enhancements for Phase II and future cavity designs.

Findings

Excluded axion models with specific coupling in 23.15-24.0 μeV range

Demonstrated operation with 9 T magnet and Josephson amplifiers

Outlined upgrades for increased sensitivity and higher frequency searches

Abstract

The HAYSTAC experiment utilizes a tunable resonant microwave cavity to search for dark matter axions. We report on the system and the results from Phase I of the experiment. This phase relied on a 9 T magnet, Josephson parametric amplifiers, and a dilution refrigerator for the operation of the experiment. Axion models with two photon coupling $\ g_{a\gamma\gamma}\gtrsim2\times 10^{-14}\ \mathrm{GeV}$ were excluded in the $\ 23.15<m_a<24.0\ \mathrm{\mu eV}$ mass range. Phase II of the experiment will include upgrades to the cryogenics system and a new squeezed-state receiver. Finally, we discuss work on multi-rod cavities and photonic band gap resonators for higher frequency operation.