Weighing the solar axion

Theopisti Dafni,Javier Galán,Krešimir Jakovčić,Gloria Luzón,Francisco J Iguaz,Igor G Irastorza,Javier Redondo,Biljana Lakić,Ciaran A J O’Hare,Elisa Ruiz Chóliz

doi:10.1103/physrevd.99.035037

Abstract

Axion helioscopes search for solar axions and axion-like particles via inverse Primakoff conversion in strong laboratory magnets pointed at the Sun. While helioscopes can always measure the axion coupling to photons, the conversion signal is independent of the mass for axions lighter than around 0.02 eV. Masses above this value on the other hand have suppressed signals due to axion-photon oscillations which destroy the coherence of the conversion along the magnet. However, the spectral oscillations present in the axion conversion signal between these two regimes are highly dependent on the axion mass. We show that these oscillations are observable given realistic energy resolutions and can be used to determine the axion mass to within percent level accuracies. Using projections for the upcoming helioscope IAXO, we demonstrate that $>3\sigma$ sensitivity to a non-zero axion mass is possible between $3 \times 10^{-3}$ and $10^{-1}$ eV for both the Primakoff and axion-electron solar fluxes.

Highlights

Axions [1,2,3,4,5] and axionlike particles [6] are low-mass pseudoscalars that are expected to couple extremely weakly to standard model fields
Three established experimental approaches use this coherent conversion: light-shining-through-wall (LSW) experiments use highintensity light sources and strong magnetic fields to produce axions in a laboratory [10,11,12], haloscopes search for relic axions that may constitute the dark matter (DM) halo of our galaxy [13,14,15,16,17,18,19,20], and helioscopes search for the axions that may be emitted by the Sun [21,22,23,24,25,26]
We have demonstrated here for the first time that helioscopes do have the capability of determining the axion mass in the vacuum mode

Summary

Introduction

Axions [1,2,3,4,5] and axionlike particles [6] (hereafter referred to as axions) are low-mass pseudoscalars that are expected to couple extremely weakly to standard model fields. The coupling of axions to two photons is of particular interest as it is guaranteed—barring any accidental cancellations—for “QCD” axions involved in the well-known solution to the strong CP problem [1,2]. This coupling is potentially observable if one is able to coherently boost axion-photon conversion inside a strong macroscopic magnetic field [7,8,9].

Methods

Results

Conclusion