A new study led by Tel Aviv University researchers demonstrates unprecedented sensitivity to an exciting dark matter candidate. As part of the new NASDUCK (“Noble and Alkali Spin Detectors for Ultralight Coherent dark-matter”) collaboration, the researchers developed unique innovative quantum technology that enables receiving more accurate information on invisible theoretical particles “suspected” of being dark matter with ultralight masses. The study was published in the prestigious Advanced Science journal.
The study was led by Prof. Tomer Volansky, research student Itay Bloch from the Raymond & Beverly Sackler School of Physics & Astronomy in the Raymond & Beverly Sackler Faculty of Exact Sciences at Tel Aviv University, Gil Ronen from the Racah Institute of Physics at the Hebrew University, and Dr. Or Katz, formerly of the Weizmann Institute of Science (now from Duke University).
Dark Matter is one of the great mysteries of physics. It composes most of the matter in the universe, and it is known to interact through gravity; however, we still know very little of its nature and composition. Over the years, many different theoretical particles have been proposed as good candidates to serve as dark matter, including the so-called “axion-like particles”.
Prof. Tomer Volansky explains: “The interesting thing about axion-like particles is that they can be significantly lighter than any of the matter particles seen around us, and still explain the existence of dark matter, which for years was expected to be significantly heavier. One of the main ways of searching for dark matter is by building a large experiment with lots of mass, waiting until dark matter collides with it or is absorbed in this mass, and then measuring the minute energetic imprint it leaves in its wake. However, if the mass of the dark matter is too small, the energy carried by it is so insignificant that neither the collision nor the absorption effect can be measured. Therefore, we need to be more creative and use other properties of dark matter.”
In order to discover these particles, the researchers have designed and built a unique detector in which compressed, polarized xenon gas is used to find tiny magnetic fields. Surprisingly, it turns out that axion-like particles which play the role of dark matter, affect the polarized xenon particles as if it is placed in a weak anomalous magnetic field which can be measured. The innovative technique used for the first time by the researchers, enabled them to explore a new range of dark matter masses, improving previous techniques by as much as three orders of magnitude.
PhD student Itay Bloch adds: “This is quite a complex operation, since these particles, if they exist, are invisible. Nevertheless, we have succeeded with this study in constraining the possible properties of axion-like particles, by the very fact that we have not measured them. Several attempts have been made to measure such particles by turning them into particles of light and vice versa. However, the innovation in our study is the measurement through atomic nuclei without relying on an interaction with light, and the ability to search for axion-like particles in masses that were hitherto inaccessible.”
The study is based on especially complex mathematical methods taken from particle theory and quantum mechanics and employs advanced statistical and numerical models in order to compare the empirical results with the theory.
Prof. Volansky concludes: “After five months of sustained effort, we have presented a new method that expands what we thought was possible with magnetometers; therefore, this is a small but significant step towards finding dark matter. There are many more candidates for dark matter, each with its own quantum properties. However, axion-like particles are among the most interesting options, and if we ever find them, that would be a huge step forward in our understanding of the universe. This experiment was the first of the NASDUCK collaboration, showing the promise that lies in our detectors. I have no doubt that this is just the beginning.”