LZ Detector Captured a Mysterious Signal That Known Physics Models Cannot Explain

Until recently, the existence of dark matter had been confirmed only by indirect astrophysical observations — through galaxy rotation curves, gravitational lensing, and cosmic microwave background parameters. However, the LZ experiment, deployed at the Sanford Underground Research Facility in South Dakota (USA), recorded a single event that does not fit any of the known scientific models. This is reported by RBC-Ukraine, citing a study published within the framework of the Sanford Underground Research Facility.

How the LZ Detector Works

To catch a unique particle, scientists built a detector at a depth of nearly 1.6 km underground. The thick layer of rock shields the instrument from cosmic radiation, while a water reservoir blocks neutrons that could produce false signals. Inside the detector is more than seven tons of ultra-pure liquid xenon. The operating principle is based on the detection of weakly interacting massive particles — WIMPs: when a hypothetical dark matter particle collides with the nucleus of a xenon atom, a brief flash of light and a stream of electrons are produced, which are then registered by the detector.

"A Needle in a Haystack": How the Signal Was Sought

Scientists compare the search for a single event against a background of random processes to looking for a "needle in a haystack." The team analyzed data from 220 days of detector operation. At the first stage, simple classical models yielded no results, but after expanding the criteria to more complex theoretical scenarios, the researchers discovered one unique event, recorded on June 16, 2023.

What the Physicists Recorded

The recorded event has a significance level of about three sigma, corresponding to a probability of a random coincidence of roughly one in four hundred. For an official announcement of a scientific discovery in particle physics, a stricter standard — five sigma — is required. The research results have already been presented at an astrophysics conference in Japan, where the team described the characteristics of the anomalous event and the method used to isolate it from the background.

Contradictory Data

Here it is important to honestly reflect the discrepancy between the media coverage and the position of the physicists themselves. On the one hand, a number of outlets characterize the event as a "breakthrough" and a possible "giving itself away" by dark matter. On the other hand, LZ collaboration spokesperson Richard Gateskill emphasizes that the team is deliberately refraining from direct claims of having detected dark matter: the three-sigma level is below the discovery threshold, and there is a possibility that an interaction of ordinary matter has been recorded, the mechanism of which scientists do not yet fully understand. Thus, there is currently no consensus on the nature of the event.

What Comes Next: Confirmation and Parallel Experiments

At present, physicists are analyzing a data set four times larger than the one collected before June 2023, which will allow them to either strengthen or refute the initial signal. Confirmation or refutation of the results is also expected in similar liquid xenon experiments being carried out in Italy and China. The combined data from several independent detectors will become the key criterion for moving from a single anomaly to a recognized scientific result.