Axions were originally proposed to explain the strong-$CP$ problem in QCD. Through axion-photon coupling, the Sun could be a major source of axions, which could be measured in solid state detection experiments with enhancements due to coherent Primakoff-Bragg scattering. The Majorana Demonstrator experiment has searched for solar axions with a set of ${}^{76}\mathrm{Ge}$-enriched high purity germanium detectors using a 33 kg-yr exposure collected between January, 2017 and November, 2019. A temporal-energy analysis gives a new limit on the axion-photon coupling as $g_{a\gamma }<1.45\times {10}^{-9}{\mathrm{GeV}}^{-1}$ (95% confidence level) for axions with mass up to $100\mathrm{eV}/c^2$. This improves laboratory-based limits between about $1\mathrm{eV}/c^2$ and $100\mathrm{eV}/c^2$.

• Received 13 June 2022
• Accepted 21 July 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.081803

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Published by the American Physical Society