Questions ‘we don’t even know’ could be answered
aims to answer the question: Are mysterious particles called neutrinos the reason we are here?
Scientists believe equal parts of matter and antimatter should have been created during the formation of the universe. But that didn’t happen, and no one knows why. Instead, the visible universe is dominated by matter. Neutrinos may be the reason why — physicists just need a bigger, well, everything to find out.
Once complete, the Deep Underground Neutrino Experiment will beam the particles 800 miles through the earth from Fermi National Accelerator Laboratory outside Chicago to Lead’s Sanford Underground Research Facility.
Sanford Underground Research Facility, which opened in 2012 after it repurposed the gold mine for scientific research, has run experiments involving neutrinos and dark matter, but nothing even close to this scale.
To embark on its grand experiment, Sanford must first expand its footprint by carving out the Long-Baseline Neutrino Facility amid tunnels that once housed the deepest and most productive gold mine in the Western Hemisphere.
Over the next 10 years, workers will remove more than 870,000 tons of rock and install a four-story high, 70,000-ton neutrino detector, while the lab’s Illinois counterpart also undergoes significant renovations.
The project will cost more than $1 billion, but scientists hope the payoff from about 12 million neutrinos per second passing through the detector will be far larger, tantamount to striking gold on a universal scale.
“If history is our guide, we may learn the answers to questions we don’t even know to ask right now,” says Bonnie Fleming, a physics professor at Yale and deputy research officer on neutrinos at Fermilab.
EVERYTHING MUST BE BIGGER
Neutrinos are tricky little things. The extremely tiny particles are among the most abundant in the universe. They don’t interact much with anything and travel close to the speed of light. In fact, 3 trillion neutrinos just flew through your body while you read the last two sentences — and that’s the big challenge for researchers.
“Maybe it makes you feel better that they only just pass through you, but if you’re actually trying to measure them, it means that you need these really intense beams and gigantic detectors to be able to have just a couple interact and measure them,” Fleming says.
Experiments already underway on neutrinos lack the sensitivity and massive scale needed when you’re essentially “looking for a needle in the haystack,” Fleming says. “To do this kind of measurement, you need all the right ingredients.”
To measure the smallest things, everything must be bigger: Scientists require more neutrinos, larger detectors, more powerful beams and a greater distance to travel, and everything needs to be deep underground to shield it from cosmic rays.
Also required: the international physics community coming together in one spot.
“Eventually you get to the scale where one organization, one science lab, one country can’t push the boundary to the next level,” says Chris Mossey, deputy director for the Long-Baseline Neutrino Facility. That’s where the scientists from more than 160 institutions come in, including Europe’s CERN, home to the Large Hadron Collider, the world’s largest and most powerful particle accelerator.
Over the next decade, they will use cutting edge, state-of-the-art technology to build the detector and create data collection systems and algorithms that capture and analyze what’s happening inside. The complicated process involves a range of tasks, including creating electronics that can function in temperatures around minus 300 degrees Fahrenheit. The reason for the “world’s largest ice box,” as Mossey puts it, is liquid argon, which requires the chilly environment.
Liquid argon, a noble gas, is what neutrinos — and antineutrinos, their counterpart, just like matter and antimatter — hit in the detector, allowing scientists to see what occurs on the rare occasion the mysterious particles interact with atoms. Differences in the numbers and properties of neutrinos vs. antineutrinos would hint at why matter dominates antimatter in our universe and show whether neutrinos played a role in its formation.
“If we don’t see a difference, there’s still a big mystery and a puzzle,” Fleming says. “If we do see something, it’s a big piece of the puzzle for why we exist.”
A TOWN IS REBORN
Before the first neutrino beam travels from Illinois to South Dakota, Lead’s decommissioned Homestake Gold Mine and some of its 370 miles of tunnels up to 8,100 feet below the surface will undergo major renovations.
Helping pave the way are former Homestake workers themselves: Half of Sanford’s staff used to work in the mine, leaving the facility with an “incredible knowledge base” to repurpose it, says Mike Headley, executive director of the lab.
Workers will shore up shafts built in the 1930s to carry miners and equipment underground. To crush and move the rock, they will construct a 3,700-foot conveyer system. Then they will install all the cutting-edge equipment that runs the experiment deep underground.
While many of the tools used for excavation to mine gold are the same as those used to sculpt the caverns that will house the neutrino detector, engineers must shift their focus to preserving the quality of the walls so they endure for decades.
“It’s like the difference between running a gravel quarry vs. building a skyscraper. You want to get it right because you want the skyscraper to last forever,” says David Vardiman, one of Sanford Lab’s lead geotechnical engineers and a former Homestake engineer with 40 years in the mining business.
The mine, which produced 41 million ounces of gold over 126 years, closed in 2002 when high production costs could no longer compete with the declining price of gold. Many citizens left town, says Vardiman, who took a severance package.
Today, change is brewing again for the 3,100 people living in the steep, rugged terrain of Lead, which receives more than 16 feet of snow on average each year and is known as a haven for outdoor sports year-round. The economic impact from Sanford Lab, the Homestake Visitor Center and now the neutrino experiment is revitalizing the community, bringing an increase in sales tax revenue and the opening of new businesses, from fast food and a brewery to a hardware store and pharmacy.
“We’re turning the corner from when the mine closed,” Vardiman says.
The overall impact from the project also will extend well beyond Lead through the creation of thousands of jobs in South Dakota and Illinois over the next 10 years, according to Fermilab’s economic analysis.
While the Department of Energy will pay for the bulk of construction, CERN and other international partners will shoulder the costs for building and designing the detector, Headley says.
“It isn’t just some big federal government project that the federal government is providing all the resources,” Headley says. “Everyone’s got a little skin in the game.”