The LUX-ZEPLIN experiment has reported a single unusual light flash in its underground detector, a possible dark matter signal that remains below the threshold required for a discovery.. The event was recorded in June 2023 in the LZ detector at the Sanford Underground Research Facility in South Dakota.
The collaboration presented the finding on Sept. 1 at the TeV Particle Astrophysics 2026 conference in Japan.. LZ said the detector contains 7 metric tons of liquid xenon and sits nearly a mile underground.
The collaboration includes 250 scientists and engineers from 39 institutions.. The team estimated a 0.5% chance, about 1 in 200, that known interference caused the signal. That corresponds to a 2.6-sigma result, below the 5-sigma standard used in particle physics to claim a discovery..
“One event, by itself, is not enough,” said Alvine Kamaha, a physics professor at UCLA and a member of the LZ collaboration.. Researchers said the event appeared at a higher energy than standard weakly interacting massive particle, or WIMP, models would predict. Henning Flaecher of the University of Bristol, part of the LZ group, said the lack of lower-energy collisions makes a standard WIMP explanation very unlikely..
Since the announcement, theorists have published many papers proposing alternatives. Several focus on a higgsino, a hypothetical superpartner of the Higgs boson from supersymmetry theory.. JiJi Fan of Brown University said the higgsino is the simplest WIMP explanation still consistent with the data.
She added that the most basic higgsino model appears to conflict with constraints from other experiments.. Other proposals point to dark matter particles from extra dimensions. Lisa Randall of Harvard University, a co-author of one such paper, said the data “looks like it’s calling out for something like this: it avoids the pre-existing constraints and fits quite naturally”..
Separately, Stefano Profumo of the University of California, Santa Cruz, introduced a framework to compare competing dark matter theories. Applying the Barbieri-Giudice measure to 12 scenarios, he found that some primordial black hole formation models ranked among the most natural of those studied, while a particle model involving Higgs boson resonance ranked among the most finely tuned..
The LZ team is now analyzing a larger dataset covering 700 days in search of more events. The researchers are also inserting synthetic events into the data during analysis and removing them only after the work is complete to reduce bias.. Independent experiments that could test the finding include the XENONnT detector in Italy and PandaX-4T in China.
“Anomalies could come and go, as we all know,” Fan said. “No matter whether the LZ event is confirmed, some of these topics would lead to long-term research.”. Featured image credit.
Tags: dark matter
