Axion and axion-like particles are considered candidates of dark matter but their detection remains elusive. They can possibly be generated in the solar interior by Primakoff scattering — interactions of photons with strong electromagnetic field. In a recent work, the CERN Axion Solar Telescope (CAST) collaboration reports new limits on the coupling constant between axions and photons obtained with their axion helioscope, which uses a dipole magnet directed at the Sun to convert axions to X-rays.

The authors collect data from the International Axion Observatory pathfinder, which has recently been upgraded with a microbulk Micromegas detector to lower the background noise and coupled with an X-ray telescope that is tuned for the detection of photons of approximately 3 keV. The background subtraction is also improved by using a xenon-based gas environment. The authors compared these data with ray-tracing simulations for a solar axion flux and an X-ray source. While the event they are searching for is absent (no axion signal), these measurements provide new constraints on the axion–photon coupling limit to be 5.7 × 10⁻¹¹ GeV⁻¹ (at 95% confidence level) for axion masses ≤ 0.02 eV. This means larger regions of the parameter space can be excluded for future axion searches.

轴子和轴子样粒子被认为是暗物质的候选者，但它们的探测仍然难以捉摸。它们可能是通过 Primakoff 散射（光子与强电磁场的相互作用）在太阳内部产生的。在最近的一项工作中，CERN 轴子太阳望远镜 （CAST） 合作报告了通过其轴子日光镜获得的轴子和光子之间的耦合常数的新限制，该轴子日光镜使用指向太阳的偶极子磁体将轴子转换为 X 射线。

作者从国际轴子天文台探路者收集数据，该探路者最近升级了 microbulk Micromegas 探测器以降低背景噪声，并结合了 X 射线望远镜，该望远镜经过调谐，可探测大约 3 keV 的光子。通过使用基于氙气的环境，背景减法也得到了改善。作者将这些数据与太阳轴子通量和 X 射线源的光线追踪模拟进行了比较。当他们正在寻找的事件不存在（无轴子信号）时，这些测量为轴子-光子耦合极限提供了新的约束，对于轴子质量≤ 0.02 eV × 5.7 ^{10-11 GeV-1}（在 95% 置信水平下）。这意味着可以排除参数空间的较大区域，以便将来的 axion 搜索。