Despite years of observations, dark matter particles have not been caught — but scientists are not stopping. We tell you how modern dark matter detectors are designed and what results their work has already brought
Why is this important?
Dark matter is a hypothetical form of matter that makes up about 27% of the mass-energy of the universe but does not emit or absorb light or interact with electromagnetic fields, making it invisible to conventional observation methods.
Its existence was proposed to explain anomalies in the universe. If you count all the visible matter in a galaxy — stars, gas, and dust — it turns out that the stars at the edges of the galaxy should be moving slowly. But in fact, they are moving faster. This means that there is something else in the galaxy, invisible, that is pulling on the stars. This invisible thing is called dark matter. It is thought to be made of unknown particles, such as weakly interacting massive particles (WIMPs) or axions.
The discovery of dark matter could revolutionize our understanding of physics, confirming or disproving theories such as supersymmetry or revealing new particles. Supersymmetry is the hypothesis that every known particle has a “partner” — a heavier superparticle. In 2025, scientists around the world are continuing to improve detectors to catch the signals of these particles. The success of these experiments could be one of the biggest scientific breakthroughs of the 21st century.
How to Search for the Invisible: Operating Principles of Detectors
The search for dark matter is one of the most ambitious tasks in modern physics. Although we cannot observe these particles directly, scientists assume that in rare cases they may interact with ordinary matter, leaving faint but detectable traces. This principle underlies the work of various detectors, each of which uses its own approach to “catching” these invisible particles.
The most common method is direct detection. It involves underground installations filled with liquid xenon or argon. If a dark matter particle collides with an atomic nucleus or electron inside the detector, it can cause a microscopic flash of light (scintillation) or ionization—the knocking out of electrons. These signals are picked up by ultra-sensitive detectors. To avoid false alarms from background radiation, such experiments are located deep underground, away from cosmic rays and other sources of noise.
Another approach is used to search for axions, hypothetical, as yet undiscovered particles that may also make up dark matter. According to one theory, axions can turn into photons, or particles of light, if they are placed in a very strong magnetic field. So to detect them, scientists create special installations with powerful magnets and sensitive materials that can detect the appearance of photons.
There are also indirect detection methods, in which scientists look not for the dark matter particles themselves, but for what remains after they decay or collide. When such particles collide and destroy each other (a process called annihilation), they can produce other particles, such as neutrinos (which are almost weightless and interact very weakly with matter), gamma rays (high-energy radiation), or even antimatter particles. These signals could come from the center of the Galaxy, the Sun, or other areas where scientists believe dark matter is especially abundant.
Cryogenic detectors use extremely cold crystals of germanium or silicon. When a dark matter particle collides with an atom in the crystal, it can release a tiny amount of heat or electrical charge—a signal that can be detected at temperatures close to absolute zero.
Finally, some scientists are betting on accelerator experiments – these are experiments at huge installations, such as the Large Hadron Collider, where particles are accelerated to near-light speed and collided with each other. Here, conditions are created for the possible birth of dark matter particles in high-energy collisions. Such events are not observed directly, but are recorded by the disappearance of energy or the deviation of particle trajectories.
In all these approaches, the main challenge remains the same: separating the extremely rare signals from much more frequent background processes, including radioactive decays, natural radiation from the Earth, and the influence of cosmic particles. To overcome these difficulties, scientists are developing increasingly sensitive and “quiet” devices that can detect the potential presence of dark matter among thousands of ordinary events.
Leading projects: what’s working right now
XENONnT: Leader in Sensitivity
XENONnT, located in the Gran Sasso underground laboratory in Italy, is one of the most sensitive detectors for searching for WIMPs and light dark matter. It uses 6 tons of liquid xenon, which produces flashes of light and ionization signals when interacting with dark matter particles.
In 2023, XENONnT set the tightest constraints yet on the interaction of light dark matter with electrons (mass less than 0.03 keV) by analyzing events with one or two electrons. These data were collected in two short runs in 2021, each lasting about a month. Although no dark matter signals were detected, the experiment significantly narrowed the range of possible parameters for light particles.
XENONnT continues to collect data, refining its techniques to suppress background noise such as radioactivity and cosmic rays. Its successes make it a leader in the race for direct detection, but the lack of signals highlights the difficulty of the task.
LUX-ZEPLIN: American heavyweight
LUX-ZEPLIN (LZ) is another powerful dark matter experiment located at the underground Sanford Laboratory in the US. It uses 7 tons of liquid xenon to search for dark matter particles called WIMPs (weakly interacting massive particles). LZ is considered cutting-edge because it is one of the most sensitive in the world for searching for heavy particles (10-100 GeV) and competes with XENONnT. It is supported by major US research centers, making it an important player in the field.
In 2023, LZ set new constraints on WIMPs: it showed that particles with masses of 10–100 GeV are unlikely to exist with certain characteristics, as they could not be captured. This helped to rule out some theories about dark matter. In 2024, LZ continued to collect data and improve its analysis methods.
Dark matter has not yet been found, but LZ is preparing for new launches in 2025 to increase the chances of discovery. LZ not only searches for dark matter, but also tests other mysteries of physics. Its results help scientists understand which particles cannot be dark matter and provide new ideas for future experiments.
PandaX-4T: China’s Breakthrough in Dark Matter Search
PandaX-4T is an experiment at the China Jinping Underground Laboratory (CJPL), the deepest in the world, which protects it from cosmic rays. It uses 3.7 tons of liquid xenon to search for dark matter, such as WIMPs and light particles. PandaX-4T is considered a breakthrough because it combines high sensitivity with cutting-edge technology: its detector detects light and electrical signals from particle collisions, and systems to clean the xenon of impurities (such as radon and krypton) reduce the background to a minimum. This allows it to search for signals that other detectors might miss. The project is supported by a team of 40 scientists, including leading universities in China.
In 2024, PandaX-4T completed an analysis of 1.54 ton-years of data (a measure of how much xenon was used and how long it took). They were looking for light dark matter particles (with masses between 0.02 and 10 MeV) that could have received energy from the Sun and collided with electrons in the xenon. They found none, but PandaX-4T set the world’s strictest limits on such particles: their interactions with electrons were weaker than previously thought, with a record limit of 3.51×10⁻³⁹ cm² for a mass of 0.08 MeV.
Also in 2024, PandaX-4T detected signals from solar neutrinos (particles from the Sun) for the first time, helping to understand how they interfere with the search for dark matter. In 2025, the project continues to collect data and improve the detector to search for WIMPs and other phenomena such as neutrinoless double beta decay. This is a hypothetical process in which two neutrons inside an atomic nucleus turn into two protons and emit two electrons — but without a neutrino, unlike normal double beta decay. Detecting it could prove that neutrinos and antineutrinos are the same particle, which would be a major discovery in particle physics.
PandaX-4T is the Chinese leader in the search for dark matter, competing with XENONnT and LZ. Its results rule out some models of light particles and help to understand how neutrinos affect experiments. The unique depth of the laboratory and the purity of xenon make PandaX-4T one of the best in the world for searching for rare signals.
Why has no one caught dark matter yet?
Despite decades of searching and impressive technological advances, scientists have yet to detect a reliable signal from dark matter. The problem is that if particles like WIMPs or axions do exist, they interact with ordinary matter so weakly and infrequently that even the most sensitive instruments could go years without detecting a single event.
Even deep underground, in isolated conditions, it is not possible to completely eliminate background noise. Radioactive decay and cosmic rays still penetrate the installations, creating signals that are difficult to distinguish from a possible trace of dark matter.
To complicate matters, physicists aren’t entirely sure what dark matter is made of. It may not include WIMPs or axions at all, but rather particles of a different nature for which existing methods simply aren’t applicable.
Moreover, the technologies used today have already reached the limits of sensitivity in some mass ranges. To take the next step, science needs new materials, new detection principles, and larger installations – perhaps even a completely new approach to the task itself.
