NuSTAR as an Axion Helioscope

TL;DR

This paper introduces a new method using NuSTAR X-ray data and solar magnetic models to set the most stringent limits yet on axion-photon coupling, exploring previously untested parameter space for axion-like particles.

Contribution

The study presents a novel solar-based axion search technique using NuSTAR data, improving existing limits on axion-photon coupling and extending the search to higher axion masses.

Findings

Established a new upper limit on axion-photon coupling $g_{a ext{ extminus} ext{photon}}$

Surpassed previous experimental constraints in the low-mass axion range

Explored axion masses up to $3.4 imes 10^{-4}$ eV

Abstract

We present a novel approach to investigating axions and axion-like particles (ALPs) by studying their potential conversion into X-rays within the Sun's atmospheric magnetic field. Utilizing high-sensitivity data from the Nuclear Spectroscopic Telescope Array (NuSTAR) collected during the 2020 solar minimum, along with advanced solar atmospheric magnetic field models, we establish a new limit on the axion-photon coupling strength $g_{a\gamma}\lesssim 7.3\times 10^{-12}$~GeV$^{-1}$ at 95\% CL for axion masses $m_a\lesssim 4\times 10^{-7}$\,eV. This constraint surpasses current ground-based experimental limits, studying previously unexplored regions of the axion-photon coupling parameter space up to masses of $m_a\lesssim 3.4\times 10^{-4}$\,eV. These findings mark a significant advancement in our ability to probe axion properties and strengthen indirect searches for dark matter candidates.