Bounds on heavy axions with an X-ray free electron laser

TL;DR

This paper reports new experimental bounds on axion-like particles in the eV to keV mass range using the EuXFEL, leveraging the Primakoff effect with higher sensitivity than previous synchrotron-based searches.

Contribution

It introduces improved exclusion bounds on ALPs by utilizing the high brightness of EuXFEL and the Primakoff effect, extending the mass range and sensitivity of previous experiments.

Findings

Established new bounds on ALPs in the 10^{-3} eV to 10^4 eV range.

Demonstrated enhanced sensitivity over previous synchrotron experiments.

Validated the use of EuXFEL for ALP searches.

Abstract

We present new exclusion bounds obtained at the European X-ray Free Electron Laser facility (EuXFEL) on axion-like particles (ALPs) in the mass range 10^{-3} eV < m_a < 10^4 eV. Our experiment exploits the Primakoff effect via which photons can, in the presence of a strong external electric field, decay into axions, which then convert back into photons after passing through an opaque wall. While similar searches have been performed previously at a 3^rd generation synchrotron, our work demonstrates improved sensitivity, exploiting the higher brightness of X-rays at EuXFEL.