Search for solar axions using Li-7

TL;DR

This paper proposes a novel method to detect solar hadronic axions emitted during Li-7 nuclear transitions, setting an upper mass limit through an experimental search involving resonant absorption.

Contribution

It introduces a new approach to search for solar axions via resonant absorption in Li-7, providing experimental constraints on axion mass.

Findings

Set an upper limit on hadronic axion mass of 32 keV

Demonstrated feasibility of resonant absorption detection method

Connected axion emission to solar neutrino observations

Abstract

We describe a novel approach to the search for solar, near-monochromatic hadronic axions, the latter being suggested to be created in the solar core during M1 transitions between the first excited level of Li-7, at 478 keV, and the ground state. As a result of Doppler broadening, in principle these axions can be detected via resonant absorption by the same nuclide on the Earth. Excited nuclei of Li-7 are produced in the solar interior by Be-7 electron capture and thus the axions are accompanied by emission of Be-7 solar neutrinos of energy 384 keV. An experiment was made which has yielded an upper limit on hadronic axion mass of 32 keV at the 95% confidence level.