TL;DR: The LUX-ZEPLIN experiment recorded one unexplained particle interaction consistent with a WIMP dark-matter signal, but researchers say it is only a hint and not a discovery.

A single flash underground sparks excitement

Researchers operating the LUX-ZEPLIN experiment, known as LZ, have reported a single particle interaction that they have great difficulty explaining with known background signals from normal matter, according to the U.S. Department of Energy. The agency said the result does not yet meet the statistical threshold required to claim a discovery, but described it as the most compelling hint of dark matter reported by the experiment to date.

The announcement centers on work presented in a scientific talk at the 2026 TeV Particle Astrophysics conference in Japan, according to the Department of Energy. The collaboration said the paper will be released on the online repository arXiv and submitted to the journal Physical Review Letters. The University of Sheffield, whose scientists participate in the collaboration, said scientists across the globe are now calling on the scientific community for help with interpreting the potentially groundbreaking findings.

LZ spokesperson Rick Gaitskell, a professor at Brown University, said the team was intrigued to see the event in the region where dark matter is expected to show up and where competing backgrounds are very low, according to the Department of Energy. He added that with only one event the team did not want to get ahead of itself, was not claiming to have seen dark matter, but had seen something interesting to share for input.

Aaron Manalaysay, a physicist at Lawrence Berkeley National Laboratory and chair of LZ's Institutional Board, said outlier events are not unexpected but usually reveal themselves as a background upon deeper examination, according to the Department of Energy. He described this as the first example in any experiment he had worked on of an outlier that appears valid in every way, while adding that the team continued to consider whether a rare background mechanism could have been missed.

Where the search took place

LZ operates nearly one mile below ground at the Sanford Underground Research Facility, called SURF, in South Dakota, according to the Department of Energy. The laboratory is managed by DOE's Lawrence Berkeley National Laboratory, known as Berkeley Lab. Reuters described the experiment as taking place about a mile, or 1.6 km, underground in South Dakota.

ABC News reported that the detector was built in an old gold mine almost 1.5 kilometres underground. That depth, combined with shielding, is central to the design because the mile of rock shields the detector from cosmic rays from space, according to the Department of Energy.

The collaboration is international in scale. LZ brings together 250 scientists and engineers from 39 institutions, according to the Department of Energy. Thirty-nine institutions of higher education and advanced research provided support, and the collaboration acknowledged the assistance of the Sanford Underground Research Facility.

Support comes from the U.S. Department of Energy, Office of Science, Office of High Energy and Nuclear Physics, and the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility, according to the Department of Energy. Additional support comes from the Science & Technology Facilities Council of the United Kingdom, the Portuguese Foundation for Science and Technology, the Swiss National Science Foundation, the Australian Research Council Centre of Excellence for Dark Matter Particle Physics, and the Institute for Basic Science, Korea.

How the xenon detector looks for WIMPs

LZ is designed to potentially detect a dark matter particle, a substance that makes up roughly 85 percent of the mass in the universe but has never been directly detected, according to the Department of Energy. The University of Sheffield used similar language, saying the mysterious substance makes up 85 per cent of the matter in the Universe and has never been directly detected. ABC News reported that scientists estimate 85 per cent of the observable universe is dark matter, known by its influence on galaxy motion but never observed directly.

The experiment uses 10 tonnes of ultrapure liquid xenon to search for dark matter and is optimized to look for WIMPs, or weakly interacting massive particles, according to the Department of Energy. The University of Sheffield said the detector is optimised to look specifically for WIMPs and described WIMPs as one of the leading dark matter candidates.

ABC News reported that the detector uses a huge vat of super-cooled liquid xenon and 494 light sensors to try to detect tiny collisions between WIMPs and normal particles. The Department of Energy said LZ searches by looking for signature flashes of light from energy deposited in the detector.

Background control involves multiple layers. Those include the rock overburden, a water tank and outer detectors that protect the central detector from background neutrons, and computational tools that disentangle particle interactions and reject dark matter mimics, according to the Department of Energy. The University of Sheffield described the same approach, including the mile of rock that shields against cosmic rays, a water tank and outer detectors that guard against background neutrons, and software tools that separate particle interactions.

Looking up into the LZ outer detector, used to veto radioactivity that can mimic a dark matter signal, was shown in an image credited to Matthew Kapust of Sanford Underground Research Laboratory, according to the Department of Energy.

A 220-day dataset and a new energy window

The LZ collaboration studies experimental data in batches, according to the Department of Energy. In the new result, researchers analyzed 220 live days of data collected between March 2023 and April 2024. ABC News described the same period as a 220-day run of the detector and reported that the single event was detected on June 16, 2023.

The team had previously searched this dataset for faint signals from the simplest kinds of WIMP interactions, according to the Department of Energy. The new analysis searched for a broader range of possible WIMP interactions that could deposit more energy in the detector. The Department of Energy said LZ is particularly sensitive to such signals while also minimizing false positives.

Sam Eriksen, a senior research associate at the University of Bristol in the U.K. and lead author of the study, said the work was a detailed study in a region not previously explored within this dataset and required months of additional effort to understand all possible causes of background events, according to the Department of Energy. He said the team understands the detector and backgrounds so well that even a single outstanding event is important, adding that dark matter events are expected to be extremely rare so only a handful could mark the first detection of WIMP dark matter.

ABC News reported that many detectors searching for WIMPs had looked at a much lower energy band based on theoretical predictions, while this detection involved a higher-energy analysis. It reported the detection had an energy range of 270 keV, implying a more massive WIMP than researchers had assumed. Jayden Newstead, a physicist at the University of Melbourne who was not involved in the research, said physicists would need to rework some theories about dark matter if the result was confirmed and that the appearance was not how dark matter had been expected to appear, according to ABC News.

Theresa Fruth, an Australian physicist on the team from the University of Sydney, said the event would not go away even after many checks, according to ABC News. Nicole Bell, a theoretical physicist at the University of Melbourne who was not involved, called it an interesting observation but said it was very early days, according to ABC News.

Why scientists call it a hint, not proof

If the anomalous event was caused by dark matter, the WIMP that generated it would likely have a mass of at least 200 GeV/c2, or more than 200 times the mass of a proton, according to the Department of Energy. It would also suggest a specific type of interaction between WIMPs and ordinary matter beyond the simplest model.

The statistical standing remains below discovery level. The LZ results have not reached 5-sigma significance, the threshold considered a discovery in physics, according to the Department of Energy. The new analysis is 2.6 sigma, meaning there is approximately a 0.5% chance that the event could be explained by known backgrounds. ABC News likewise reported 2.6 sigma and a 0.5 per cent chance the event could be explained by known backgrounds, and said the team examined background interference such as neutrons and neutrinos but found none could be identified as a likely explanation.

The University of Sheffield quoted Professor Dan Tovey, leader of the LZ team at Sheffield, saying that with just one event it is not possible to conclude that the team is seeing first signs of new physics, but if that were the case the consequences for understanding the universe would be profound. He said a huge amount of work had checked whether the event was due to more mundane processes and that so far it had passed every test, adding that only more data could provide certainty.

ABC News noted that no other detector has provided concrete evidence for dark matter and most have found nothing at all, except the DAMA/LIBRA experiment in Italy, which found an annual signal it attributes to dark matter but which no other detector has confirmed after years of attempts. Bell said the signal detected by LUX-ZEPLIN was very different but perhaps easier to explain as dark matter, according to ABC News.

What comes next for verification

With additional data, researchers can test whether the finding grows in significance or fades away, according to the Department of Energy. LZ has already accumulated the world's largest dark matter dataset and will continue to accrue WIMP search data at SURF, substantially improving search statistics.

The collaboration explicitly invited broader scrutiny. Gaitskell said the team wanted to share the result with the scientific community for its input, according to the Department of Energy. The University of Sheffield said the paper will be released on arXiv and submitted to Physical Review Letters, the same publication plan described by the Department of Energy.

ABC News reported that the results were released for other scientists to examine, with researchers hoping other detectors will be able to find similar events in their data. Bell said that if the signal is really dark matter more events will appear soon and that would be a huge breakthrough, according to ABC News.

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