LZ Experiment Sees Surprising Result In Search For Dark Matter

New submitter greytree shares a report from Brown University: LUX-ZEPLIN, an experiment co-led by Brown University faculty and students, observed a particle interaction that could be interpreted as a signal from WIMPs, a dark matter candidate -- but researchers need more data to confirm.

[...] The result does not yet meet the statistical threshold required to claim a discovery, but it is the most compelling hint of dark matter reported by the experiment to date.

"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 Rick Gaitskell, a professor of physics at Brown University and the spokesperson for LZ. "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." [...] 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.

The LZ results have not reached "5-sigma" significance, the statistical threshold in physics that an event must reach to be considered a discovery. The new analysis is 2.6 sigma, meaning there is approximately a 0.5% chance that the event could be explained by known backgrounds. 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. JiJi Fan, an associate professor of physics at Brown not involved in the LZ experimental research but whose theoretical work is cited in the new LZ paper, said the new findings were "very intriguing."

While the event recorded by LZ could not have been the simplest type of WIMP interaction, there are other types of possible interactions that could explain it, she said. Had a WIMP interacted in the simplest way at the high energy associated with this recent event, the detector would have recorded many recoil events at lower energies following the initial event.

LZ recorded a single event, however, which requires an expanded theoretical explanation. "There are well-motivated theoretical extensions, including inelastic scattering and momentum-dependent elastic scattering, that could potentially account for this single event," Fan said.

"This also sets up a target for on-going dark matter hunting, not only at direct detection experiments such as LZ but also at other complementary experimental frontiers." The results were presented in a scientific talk at the 2026 TeV Particle Astrophysics conference in Japan on Tuesday, Sept. 1. A paper detailing the finding can be found here (PDF).