Probing the axion-nucleon coupling with the next generation of axion helioscopes

TL;DR

This paper explores how next-generation axion helioscopes can detect axions produced by nuclear processes in the sun, significantly improving the sensitivity over previous experiments and probing the axion-nucleon coupling.

Contribution

It revises the solar axion flux bounds and assesses the enhanced detection capabilities of IAXO and BabyIAXO for axions from Fe-57 isotopes.

Findings

BabyIAXO surpasses previous solar axion search sensitivities.

IAXO can improve detection sensitivity by over an order of magnitude.

The study discusses model dependence of the axion signal.

Abstract

A finite axion-nucleon coupling, nearly unavoidable for QCD axions, leads to the production of axions via the thermal excitation and subsequent de-excitation of Fe-57 isotopes in the sun. We revise the solar bound on this flux adopting the up to date emission rate, and investigate the sensitivity of the proposed International Axion Observatory IAXO and its intermediate stage BabyIAXO to detect these axions. We compare different realistic experimental options and discuss the model dependence of the signal. Already BabyIAXO has sensitivity far beyond previous solar axion searches via the nucleon coupling and IAXO can improve on this by more than an order of magnitude.