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A record-breaking investigation, utilizing a particle detector a mile underground in South Dakota, might have revealed new insights about darkish matter, the mysterious substance believed to make up a lot of the matter within the universe.
Utilizing the most important dataset of its variety, the experiment — referred to as LUX-ZEPLIN (LZ) — constrained the potential properties of one of many main candidates for darkish matter with unprecedented sensitivity. The analysis didn’t uncover any proof of the mysterious substance, however will assist future research keep away from false detections and higher hone in on this poorly understood piece of the universe.
WIMPs vs. neutrinos
The group had two targets for the brand new research: to elucidate the properties of a low-mass “taste” of proposed dark-matter particles referred to as weakly interacting huge particles (WIMPs), and to see if the detector might view photo voltaic neutrinos — almost mass-less subatomic particles produced by nuclear reactions contained in the solar. The group suspected that the detection signature of those particles might be just like that predicted by sure fashions of darkish matter, however wanted to identify the photo voltaic neutrinos to know for certain.
Earlier than the experiment, which took 417 days to carry out between March 2023 and April 2025, the detector’s sensitivity was upgraded to seek for uncommon interactions with elementary particles. A cylindrical chamber stuffed with liquid xenon was the theater for motion. Researchers might look ahead to both WIMPs or neutrinos colliding with the xenon, both of which produces flashes of photons, together with positively charged electrons.
The experiment pushed ahead the science for each the WIMP and neutrino questions. For the neutrinos, researchers improved their confidence {that a} sort of photo voltaic neutrino, often known as boron-8, is definitely interacting with the xenon. This data will assist future research keep away from false detections of darkish matter.
Physics discoveries usually should attain a confidence stage referred to as “5 sigma” to be thought of legitimate. The brand new work achieved 4.5 sigma — a substantial enchancment over sub-3-sigma outcomes reported in two detectors final yr. And that was particularly notable on condition that boron-8 detections occur solely about as soon as a month within the detector, even when monitoring 10 tons of xenon, Gaitskell stated.
As for the darkish matter query, nevertheless, the researchers did not discover something definitive for the low-mass kinds of WIMPs they have been searching for. Scientists would have recognized it in the event that they noticed it, the group stated; if a WIMP hits the guts of a xenon molecule, the vitality of the collision creates a particular signature, as finest as fashions predict.
“In the event you take a nucleus, it’s attainable for darkish matter to come back in and truly concurrently scatter from all the nucleus and trigger it to recoil,” Gaitskell defined. “It is often known as a coherent scatter. It has a selected signature within the xenon. So it is these coherent, nuclear recoils that we’re searching for.”
The group didn’t detect this signature of their experiment.
Doubling the run
One other, longer run will start in 2028, when the detector is anticipated to gather outcomes for a record-breaking 1,000 days. Longer runs give researchers a greater likelihood of catching uncommon occasions.
The detector will hunt not just for extra photo voltaic neutrino or WIMP interactions but additionally different physics which will fall outdoors the Normal Mannequin of particle physics stated to explain a lot of the atmosphere round us.
Gaitskell emphasised that the function of science is to maintain pushing ahead even when “damaging” outcomes come up.
“One factor I’ve discovered is, do not ever assume that nature does issues in the way in which that you simply assume it ought to, precisely,” stated Gaitskell, who has been learning darkish matter for greater than 4 many years.
“There are many elegant [solutions] that you’d say, ‘That is so stunning. It needs to be true.’ And we examined them … and it turned out, nature ignored it and nature didn’t need to go down that specific route.”
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