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Sunday, September 26, 2021

Team of scientists receives grant to design world’s largest neutrino detector

In our universe, matter and antimatter should be present in equal amounts, according to the laws of physics. But they’re not. In fact, most of the visible universe appears to be matter.

Further, matter and antimatter obliterate each other upon contact. So, had they been present in equal amounts immediately following the Big Bang, the expansion of the universe would have been stopped then and there – its intensification extinguished on the spot. We would not be.

Neutrinos, sometimes called “ghost” particles, may hold the key to this cosmology conundrum.

As such, the National Science Foundation has recently awarded $4.4 million to a team of scientists led by UC Davis physics professor Robert Svoboda to design the world’s largest neutrino detector.

“If we get the funding for the design, this will be the biggest and brightest neutrino experiment in the world,” Svoboda said.

The detector will be 15 times bigger than the Super-Kamiokande detector in Japan, currently the largest one in the world. It will be housed 4,800 feet below ground in an old goldmine in South Dakota and will cost about $500 million, according to a press release.

A neutrino beam will also be located at Fermilab, a U.S. government laboratory west of Chicago. There, the beam will create and shoot neutrinos and antineutrinos 800 miles to the detector in South Dakota. The beam will cost approximately $300 million.

“Nothing of this scope has ever been done,” said Regina Rameika, Fermilab project scientist. “We’re talking about a project that approaches a billion dollars.”

And it’s a price tag that doesn’t even include the construction of a tunnel from Illinois to South Dakota.

Well, that’s because neutrinos don’t actually need a tunnel.

Less than one-millionth the mass of electrons, the next smallest particle, neutrinos travel at almost the speed of light, statistically very unlikely to ever interact with the earth or any other matter, Svoboda said.

Neutrinos are generated from the sun, cosmic rays, nuclear reactors and radioactive decay from Earth’s core. From the sun alone, 100 million neutrinos bombard about the area of a human thumb every second. But only one, approximately, will interact with a person in his lifetime.

“Except for light, they are the most abundant particle in the universe,” Svoboda said. “But no one would ever know it.”

And it is in this ubiquity, along with their unique physical properties, that neutrinos may explain the matter-antimatter dissymmetry.

“About a decade ago, this information was sort of controversial, not very well understood,” said Mani Tripathi, UC Davis physics professor. “But now there is very little controversy, if any at all, in this type of physics. Particle physicists put themselves through the ringer.”

There are three types of neutrinos, each of which has a slightly different mass. As they travel, each type of neutrino “oscillates” or morphs itself into another.

Due to this unique oscillation, neutrinos may greatly impact matter-antimatter symmetry in favor of matter. Scientists will investigate this property.

When the particles created at Fermilab in Illinois reach the detector in South Dakota, sensors will analyze the light signature left by the particles as they travel through ultrapure water. This will give the scientists a better understanding about neutrino speed, movement and orientation.

The project will take place thousands of feet underground in an effort to isolate the neutrinos under scrutiny. Otherwise, other neutrinos from other sources could potentially disrupt the data, Rameika said.

“From this project, we may be able to paint a picture of the early stages of the Big Bang,” she said. “These ghostly particles may be able to tell us a lot about our early universe.”

The timetable on the project, as well as the effort required from scientists around the country, is extensive. The design phase of the project will run until about 2012 and, if the National Science Board approves the design, the experiment could begin in 2017. The project would employ over 500 physicists and even more engineers and technicians, Svobada said.

“The United States hasn’t seen anything like this in physics in a very, very long time,” Rameika said. “The pay off for this will be enormous.”

DAVID LAVINE can be reached at campus@theaggie.org.


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