AUSTIN (KXAN) — The most sensitive dark matter detector in the world is showing results in the hunt for the hypothetical particle. The results: they can’t find it.
“If you think of the search for dark matter like searching for buried treasure,” said Scott Kravitz, an associate professor in the physics department at the University of Texas, “we’ve basically dug part of the way down to where it might be, it could still be deeper below what we’ve searched so far.”
(Credit: Matthew Kapust/Sanford Underground Research Facility)
Kravitz is part of the LEX-ZEPLIN project, a Department of Energy hunt for dark matter in a cavern in South Dakota.
“We have a really big particle detector filled with seven tons of this element called Liquid Xenon that we put a mile deep in a mount in a mine in South Dakota. So we put it in this really quiet environment, far removed from background interactions, so that we can see even the slightest hint of dark matter interactions in our detector,” Kravitz said.
Dark matter matters
Dark matter is a hypothetical particle that scientists believe makes up 85% of our universe. Traditional mass (planets, stars, humans, etc.) only makes up around 5% of the universe.
Scientists believe that dark matter exists because of gravity. Objects in orbit of one another in our universe show signs that something is having a gravitational effect on them that’s greater than the mass of the objects around them.
Something has to be the cause. Scientists think that dark matter, which does not emit, reflect or absorb light, is this thing.
“So far, our attempts to observe it directly here on Earth, instead of through astronomical observations, we haven’t come up with any observations yet,” Kravitz said.
There are a couple theories about what dark matter is exactly. One theory is that it is actually super tiny primordial black holes.
LZ and the WIMP
The team is searching for one theoretical form of dark matter: WIMPs. WIMP stands for Weakly Interacting Massive Particles. They are believed to be super tiny particles that only have a slight effect on other matter.
The detector was unable to find any WIMPs since it was activated in 2021.
Kravitz said that the experiment isn’t a loss. “Despite not detecting dark matter, we’ve actually still learned something very important about dark matter, which is that it’s we’ve greatly ruled out the range of places that dark matter could be hiding.”
(Credit: Stephen Kenny/Sanford Underground Research Facility)
Buried a mile deep beneath the Earth to limit interference from cosmic rays, LZ uses 10 tons of liquid xenon that dark matter can bump into.
“We’re hoping that with a very sensitive particle detector like what we have with LZ, we can occasionally observe an interaction of a dark matter particle with our detector,” Kravitz said.
LZ will operate until 2028. Researchers plan to collect 1,100 days worth of data in the hopes of finding dark matter.
“If we don’t see anything in the next couple of years, we’re already working now to collaborate with a wider group of other dark matter physicists to form a collaboration to make basically the ultimate dark matter detector,” Kravitz said.