Scientists detect possible dark matter interaction

An international team of scientists has potentially detected the very first hint of a dark matter interaction, in what appears to be the most compelling indication of this mysterious invisible substance to date. That’s according to data presented this week at the TeV Particle Astrophysics 2026 conference, now available as a pre-print for wider scrutiny by the scientific community.

First proposed nearly a century ago, dark matter accounts for around 85% of the mass in the universe but has never before been directly detected. The new study, which involved an international collaboration of 250 scientists and engineers from 39 institutions spanning six countries, recorded a single particle interaction, which researchers have struggled to explain with known background signals from normal matter.

For two years, the team have been rigorously scrutinising data from the LUX-ZEPLIN (LZ) dark matter detector, managed by the US Department of Energy’s Lawrence Berkeley National Laboratory, which operates nearly a mile underground at the Sanford Underground Research Facility (SURF) in South Dakota. The study, using data collected from LZ, found one particle interaction which could potentially have been caused by a weakly interacting massive particle (WIMP), a candidate for dark matter.

LZ searches for dark matter by looking for signature flashes of light from energy deposited in the detector. The collaboration leverages multiple methods to prevent or account for particle interactions caused by normal matter. This includes the mile of rock that shields the detector from cosmic rays from space, a water tank and outer detectors that protect the central detector from background neutrons, and a suite of computational tools that disentangle particle interactions and reject dark matter mimics.

The experiment, which is ongoing, used 10 tonnes of ultrapure liquid xenon to search for dark matter and is optimised to look for WIMPs. The LZ collaboration studies experimental data in batches; in the new result, researchers analysed 220 live days of data collected between March 2023 and April 2024. The collaboration had previously searched this dataset for faint signals from the simplest kinds of WIMP interactions, while the new analysis searched for a broader range of possible WIMP interactions that could deposit more energy in the detector. LZ has been designed and constructed to be particularly sensitive to such signals while also minimising false positives. Statistically, there’s around a one in 200 chance this is a false positive result.

“This was a detailed study in a region we hadn’t explored within this dataset, and we spent months of additional effort to understand all the possible causes of background events,” said lead author Dr Sam Eriksen, Senior Research Associate at the University of Bristol, who presented the data.

“We understand our detector and the backgrounds so well that even a single outstanding event, like the one we found, is important. We expect dark matter events to be extremely rare, so only a handful could mark the first detection of WIMP dark matter.”

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 (gigaelectronvolts), or more than 200 times the mass of a proton. It would also suggest a specific type of interaction between WIMPs and ordinary matter beyond the simplest model.

The LZ results have not reached ‘5-sigma’ significance, the statistical threshold considered a discovery in physics. The new analysis is 2.6 sigma, meaning there is approximately a 0.5% chance that the event could be explained by known backgrounds.

“We’re very intrigued to see this event in the data, in the region where we expect dark matter to show up, and the competing backgrounds are very low,” said LZ spokesperson Professor Rick Gaitskell, from Brown University.

“With only one event, we don’t want to get ahead of ourselves. We are not claiming to have seen dark matter. But we have seen something interesting that we want to share with the scientific community for their input.”

With additional data, researchers can test whether the finding continues to grow in significance or fades away. LZ has already accumulated the world’s largest dark matter dataset and will continue to accrue WIMP search data at SURF, substantially improving their search statistics.

Image caption: To search for dark matter, LZ uses photomultiplier tubes (shown here before installation in the detector) to capture light from particle interactions. Image credit: Matthew Kapust/Sanford Underground Research Laboratory.