Physicists announce progress in research on underground particles in lead
The attached interviews are from SDPB’s daily public affairs show, In the Moment, with Lori Walsh.
Progress at Sanford’s underground lead research facility – including an experiment that recently began – could give physicists insight into the building blocks of the universe.
The facility, which was previously a gold mine, houses experiments such as the LUX-ZEPLIN (LZ) dark matter experiment and the Deep Underground Neutrino (DUNE) experiment.
“The world’s most sensitive dark matter experiment”
Hugh Lipincott on In the Moment
Hugh Lippincott is assistant professor of physics at the University of California, Santa Barbara
The LZ detector was brought online two months ago. It is used to search for dark matter, a theoretical concept whose physical proofs have eluded physicists for decades. Hugh Lippincott is the spokesperson for the experiment.
“Nothing we see in space and astrophysical observations makes sense if you don’t include a dark matter component,” Lippincott said. “It’s this essential part of how our universe has come to be as it is, but we’ve never really seen what it is itself.”
Physicists at the facility are trying to prove a theory about the fundamental nature of dark matter.
“Our main hypothesis is that dark matter is a particle. If this hypothesis is correct, then our galaxy is permeated with dark matter particles,” Lippincott said. “It’s a new type of particle that has never been seen before in physics.”
Physicists hope that a particle of dark matter will “bump” on their detector, which Lippincott says is “essentially a giant bucket of xenon.” The density of xenon means it can block environmental radiation. When hit by a particle, xenon creates flashes of light that can be detected by researchers.
The LZ detector is a larger version of an earlier experiment that failed to prove the existence of dark matter. Preliminary data collected this year showed that the new detector is the most sensitive in the world. But Lippincott says they can’t be sure it will be successful this time around.
“There are no guarantees,” he said. “I think it’s less than 50/50, just because there are so many other possibilities and this is just one of them.”
If they find evidence of dark matter, he says, “someone is going to get a Nobel Prize.”
The experiment will collect data over a period of five years. A similar program is underway at a site in Italy.
Claire David on In the Moment
Claire David is an assistant professor of physics at York University.
Detection of deep underground neutrinos
Along with the search for dark matter, scientists are also building a neutrino detection project. Workers excavate rock from the caverns of the facility to prepare for the experiment.
“The scale of this excavation is truly incredible,” said Mike Headley, executive director of the Sanford Underground Research Facility. “If you can imagine a loaf of bread 500 feet long, 90 feet high, 60 feet wide, that’s really the size of one of the two caverns.”
The experiment will help scientists learn more about neutrinos, which are tiny subatomic particles.
“We’re going to learn a lot more about the particle itself, but also about the role it plays in the universe,” said physicist Claire David.
Neutrino bunches will be fired from a facility in Chicago. The particles will then travel 800 miles through the underground rock to the lead.
“If we study them near beam production, near Chicago, and then at SURF after that 800-mile trip, we’ll see how much flavor they change over time,” David said. “It gives us a lot of answers about their behavior and physics.”
Neutrinos will make the trip in less than a second.
The experiment will also be sensitive to particles released by astronomical events, such as supernova explosions.
“It’s actually an underground telescope,” David said. “It is good to put it in the ground, to protect it from the background [radiation] that we don’t want, and then do astronomy from there.
The project will be used to test theoretical physics ideas related to neutrinos. David said the experimental results could be compared with results from a similar facility in Japan, which has a different design.
The excavation is expected to be completed in 2024. The project will not be fully operational until the 2030s.