Our Take
The field's shift from narrow WIMP consensus to 50 orders of magnitude of candidate particles reflects not progress but the absence of it—and the next experiment may be unfunded.
Why it matters
The US Department of Energy withdrew funding from XLZD, a $300M+ detector that would have been the final large-scale WIMP hunt. This matters to physicists because it marks the end of a 40-year experimental strategy and forces a reset on where to look next.
Do this week
Particle physics experimentalists: map your detector's sensitivity against the 50-order-magnitude candidate space published in 2022 so you can identify which parameter range your lab is actually constraining.
The neutrino fog blocks the old path
Three massive detectors—buried beneath the Apennines, Jinping Mountains, and a South Dakota mine—were built to catch WIMPs, hypothetical particles that theorists expected to compose dark matter. After years of running, they detected signals. But not from WIMPs. Instead, they picked up neutrinos from the sun and stars, rare interactions that act as noise drowning out any dark matter signal.
The detectors are so sensitive they have entered what physicists call the neutrino fog. There is no shielding from neutrinos; they pass through Earth itself. The next generation WIMP experiment, XLZD, would have used 60 to 80 metric tons of liquid xenon—roughly the planet's yearly production—to push past this limit. In December 2025, the US Department of Energy announced it would not fund XLZD or contribute to its cost, potentially over $300 million. "It may be that the project doesn't happen at all," says Hugh Lippincott, who leads the LZ detector at Homestake Mine.
The consensus candidate collapsed, and funding collapsed with it
WIMPs emerged in the 1980s as a two-for-one solution. Theorists building add-ons to the standard model of particle physics proposed supersymmetry, which paired each known particle with an unseen superpartner. These superpartners would be massive, weakly interacting—ghostlike—and could solve the dark matter problem. For 30 years, this was the dominant working hypothesis.
The Large Hadron Collider, operational since 2008, did not find superpartners. Meanwhile, WIMP detectors found nothing either. The motivation to hunt has not weakened (we know dark matter is 83% of the matter in the universe), but the strategy has collapsed.
Physicists have begun exploring candidates across 50 orders of magnitude in mass: from primordial black holes (asteroid-sized objects formed near the Big Bang) to axions (particles a trillionth to a millionth the mass of an electron). They have combed perhaps 10 to 20 percent of the parameter space for axions alone. Experiments like MADMAX and ABRACADABRA use ultracold chambers and quantum sensors to listen for axions converting to photons. Others propose liquid-helium detectors and atmospheric searches. There is no consensus on where to look next, no single bet that justifies a $300 million commitment. The field has fragmented into a portfolio of smaller, cheaper, more speculative efforts.
Know the mass range your experiment can actually constrain
If you run a dark matter detector or design one, publish which slice of the 50-order-magnitude candidate space your apparatus has sensitivity to. The field's transition from a unified hunt to a scattered one means clarity about what each experiment rules in or out is now the only shared currency. Without that framing, individual detectors become isolated effort rather than coordinated constraint on dark matter's properties.