Dark matter may finally be coming into focus thanks to a recent LUX-ZEPLIN (LZ) experiment, which detected a particle interaction that is difficult to explain as arising from ordinary matter.
Physicists believe that 85% of the matter in the universe is dark matter rather than ordinary matter, but because it neither emits nor reflects light, the mysterious substance effectively remains invisible.
The new findings, described in a recent paper submitted to Physical Review Letters and in a talk at Japan’s 2026 TeV Particle Astrophysics conference, detail the work of dozens of researchers that may constitute an intriguing hint in advance of a confirmed dark matter detection.
LUX-ZEPLIN
A massive international team of 250 scientists and engineers across 39 institutions makes up the LZ project, which conducts its experiment at a facility in South Dakota, almost a mile below ground. This facility, the Sanford Underground Research Facility (SURF), houses the detector, which is optimized to search for weakly interacting massive particles (WIMPS), one of the primary candidates for dark matter.
It does so using ten metric tons of ultrapure liquid xenon in a cylindrical detector. Layers surrounding the chamber block or detect background particles during the dark matter search. If WIMPs collide with xenon atoms, they should produce tiny flashes of light and electrons that can be detected within the chamber.
The nearly mile of rock above the facility helps prevent cosmic rays and other surface radiation from interfering with the experiments. A water tank and outer detectors help shield the central detector from background neutrons, while computational tools separate particle interactions to identify events that may mimic a dark matter observation.
Dark Matter Data
“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 Sam Eriksen, a senior research associate at the University of Bristol in the UK.
“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,” Eriksen added.
Measurements used in the study were collected between March 2023 and April 2024, totaling 220 live days. The new work wasn’t the first pass on this dataset, as researchers had previously searched it for faint signals from the simplest kinds of WIMP interactions. This time, the team expanded its search to a broader range of possible interactions that could deposit more energy in the detector.
A Possible Dark Matter Detection
“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 Rick Gaitskell, a professor at 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.”
According to researchers, the event was an outlier from other LZ measurements and is consistent with one of the dark matter models the team explored. However, increasingly sensitive technology can ironically reveal previously unseen background processes alongside potentially interesting new signals. The sensitivity of the detectors used at LZ may therefore be measuring a background that earlier instruments missed rather than dark matter.
This detection is rated at 2.6 sigma, about half of the 5-sigma threshold needed to ensure the signal is not background noise. Further observations will be needed to push certainty toward that 5-sigma goal, but this could be a major step in that direction.
The paper, “Search for Dark Matter Particle Interactions in an Extended Nuclear Recoil Energy Window with the LUX-ZEPLIN (LZ) Experiment,” is currently available on the LUX-ZEPLIN website.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.