Search for solar axions via axion-photon coupling with the Majorana Demonstrator

TL;DR

This paper reports a search for solar axions using germanium detectors in the Majorana Demonstrator, setting new limits on axion-photon coupling strength for axion masses up to 100 eV/c^2.

Contribution

It presents the first search for solar axions with the Majorana Demonstrator, improving laboratory limits on axion-photon coupling in the 1-100 eV mass range.

Findings

Set a new upper limit on axion-photon coupling: g_{aγ}<1.45×10^{-9} GeV^{-1}

Achieved improved constraints over previous laboratory limits for axion masses 1-100 eV

Utilized a 33 kg-yr exposure with germanium detectors from 2017 to 2019

Abstract

Axions were originally proposed to explain the strong-CP problem in QCD. Through the 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 $^{76}$Ge-enriched high purity germanium detectors using a 33 kg-yr exposure collected between Jan. 2017 and Nov. 2019. A temporal-energy analysis gives a new limit on the axion-photon coupling as $g_{a\gamma}<1.45\times 10^{-9}$ GeV$^{-1}$ (95% C.I.) for axions with mass up to 100 eV/$c^2$. This improves laboratory-based limits between about 1 eV/$c^2$ and 100 eV/$c^2$.