First results from a microwave cavity axion search at 24 micro-eV

TL;DR

This paper presents the initial results of a microwave cavity experiment searching for dark matter axions around 24 micro-eV, achieving unprecedented sensitivity and quantum-limited noise performance.

Contribution

First to reach cosmologically relevant sensitivity in the 20-25 micro-eV axion mass range using advanced quantum-limited amplification techniques.

Findings

Excluded axion-photon coupling $g_{a\gamma\gamma} \\gtrsim 2\times10^{-14}~\text{GeV}^{-1}$ in 23.55-24.0 micro-eV range.

Achieved total noise near the standard quantum limit with dilution refrigerator and Josephson parametric amplifier.

Demonstrated the feasibility of quantum-limited axion searches at higher masses.

Abstract

We report on the first results from a new microwave cavity search for dark matter axions with masses above $20~\mu\text{eV}$. We exclude axion models with two-photon coupling $g_{a\gamma\gamma} \gtrsim 2\times10^{-14}~\text{GeV}^{-1}$ over the range $23.55~\mu\text{eV} < m_a < 24.0~\mu\text{eV}$. These results represent two important achievements. First, we have reached cosmologically relevant sensitivity an order of magnitude higher in mass than any existing limits. Second, by incorporating a dilution refrigerator and Josephson parametric amplifier, we have demonstrated total noise approaching the standard quantum limit for the first time in an axion search.