Chinese Scientists Finally Prove a Forgotten 1930s Theory — Key Find for Dark Matter Research

Nearly 90 years ago, a Soviet physicist, Arkady Migdal, introduced a revolutionary idea. Now, for the very first time, Chinese scientists directly observed it. Uncovering this theory, called the “Migdal effect,” could help researchers understand the mysterious substance that is called dark matter. It is described as the ‘glue’ of the universe that helps it hold itself together. However, for decades, the Migdal effect existed only on paper. But a research team from the University of the Chinese Academy of Sciences (UCAS) used advanced experimental equipment to observe the effect directly. “Dark matter, an invisible yet gravitationally interacting component of the universe, remains one of the most profound unsolved mysteries in modern physics,” the team said in a published paper from a peer-reviewed journal Nature.

According to the Migdal effect, when a neutral particle, such as dark matter, collides with the nucleus of an atom, the collision would not only cause the atomic nucleus to recoil, but would also knock loose an electron. That secondary reaction would produce a small but measurable signal that scientists could use to spot the otherwise undetectable particles. However, the theory was long forgotten and the team said that conversations surrounding it dated back to the mid-2000s. Zheng Yangheng, corresponding author of the paper and a professor at UCAS, said, “For more than 80 years, the Migdal effect in neutral particle collisions had never been directly confirmed by experiments.”

The Chinese research team found direct proof of the Migdal effect and said, “In this study, we present the direct evidence of the Migdal effect in neutron-nucleus scattering – a phenomenon predicted more than 80 years ago but confirmed only now with a statistical significance exceeding 5 sigma.” 5 sigma is a statistical standard that strongly suggests that the findings are not caused by chance and are real. “By validating the Migdal effect, we address a long-standing gap in the scientific understanding of fundamental interactions and offer a potential approach for the detection of light dark matter,” the team added. 

The team further explained that they built a gaseous pixel detector capable of capturing both nuclear recoil and Migdal electron tracks for the experiment. A mixture of 40% helium and 60% dimethyl ether was used, and it was blasted with neutrons to trigger the effect. The effect was captured by a charge-sensitive pixel array chip. The team collected data for almost 150 hours, collected data from 100 events, and narrowed it down to 6 strong candidates that fit the requirements. “This result establishes a crucial benchmark for nuclear and particle physics, providing an experimental foundation for future theoretical and experimental investigations,” the researchers said.

Dark matter is one of the most mysterious substances, and scientists believe it makes up 27% of the universe. It does not emit, reflect, or absorb light, which is why it is called “dark.” Because of this, even the most powerful telescopes cannot detect it in the usual way. Although it cannot be seen, the existence of dark matter is essential because of its gravitational effects. Galaxies rotate much faster than they should, and if an unseen force were not holding them together, these galaxies would fly apart. Dark matter is believed to provide that extra gravity, acting like an invisible glue. So far, no dark matter particle has been directly detected by scientists, despite decades of effort. Previously, the focus was on searching for heavy dark matter particles, but they have also not given conclusive results. The Migdal effect offers a promising solution, and researchers could be closer to understanding the laws of the universe.

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