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Fermi National Accelerator Laboratory

Fermilab creates neutrinos using a high-energy proton beam and plans to  funnel them 900 miles to a detector in South Dakota's Sanford Underground Research Facility.

Fermilab revs up search for the elusive neutrino

by Rebecca Halleck
May 23, 2013

Neutrinos, perhaps the slipperiest of the known subatomic particles, don't stop traffic.

They have minimal environmental impacts but their impact on the cosmos could answer an ages-old question: why do we exist?

The Fermi National Accelerator Laboratory in Batavia will host an informational meeting tonight to discuss its proposed Long-Baseline Neutrino Experiment. As with all research funded by the Department of Energy, Fermilab is required to submit an environmental assessment as part of their approval process. Though the lab won’t be formally filing the assessment until 2014, researchers want to start the conversation with community members early.

“We like to be good neighbors,” said Katie Yurkewicz, director of communications at Fermilab. The neutrino science team doesn’t anticipate environmental impacts beyond minor construction noise and slight increases in traffic for nearby residents as facilities expand to incorporate a new experiment,  according to Yurkewicz.

Though the environmental impacts could be nearly as small as the neutrinos, the resulting research would be galactic. Understanding how neutrinos operate could eventually help physicists explain the imbalance between matter and antimatter in our universe, getting us one step closer to identifying our origins, according to Jim Strait, Fermilab's project director. And it could also lead to other inventions along the way.

“Basic research has had huge impacts that people are not really aware of,” said Strait. “The microcircuits could not have been invented without an understanding of quantum mechanics—it was studied and first theorized 80 or 90 years ago. And if you’d asked people in 1925 studying quantum mechanics, they wouldn’t have had any idea what purpose it would serve, but can you imagine a world without transistors?” He also noted that the Internet was invented by physicists trying to find a place to store and share their data.

The newest neutrino experiment is an expansion of research the lab was already conducting with its Main Injector Neutrino Oscillation Search—MINOS. Both experiments examine the behaviors of the elusive neutrino, which has a habit of slipping through researchers fingers like sand. They are near massless, after all.

We are bathed in millions of neutrinos by the second. They are created naturally by both our atmosphere and the sun, surrounding and passing through us undetected at all times. They can also be created and harnessed by high-energy proton beams such as the one already in use at Fermilab.

A neutrino beam is made by smashing particles against a carbon target, creating a subatomic shower of charged particles. These particles are funneled using magnets, and they decay into the chargeless neutrinos which pass through the earth toward distant detectors.

The proposed detector for the future experiment would be in South Dakota at the Sanford Underground Research Facility. The neutrinos will cross the almost 900 mile distance in a fraction of a second. They require no pipe, wire or other medium to travel because they are so light that even gravity barely affects them—allowing them to pass through the earth like a jet through air.

The neutrinos spread as they travel. “It’s like holding a piece of paper up to a flashlight,” said Debbie Harris, a veteran of Fermilab’s MINOS project that hurls neutrinos to an underground steel target in Minnesota.

“When the flashlight is closest to the paper, the circle of light is smaller than if you pulled the paper further away.” That's why, at Fermilab, the MINOS neutrinos start on their path in a stream about 6 feet across. But, at the other end of the on-going experiment, the detector for the particles is 6,562 feet, roughly two kilometers wide.

The most significant difference between the MINOS experiment and the upcoming research will be the detectors at two end sites - Minnesota and South Dakota, according to Harris. The new experiment will deadend at a tank containing 10,000 tons of frigid liquid argon to receive the neutrinos.

In its liquid state, argon is denser than water and has more nuclei packed into the confined space—this is significant because the scientists are hoping to observe the neutrinos’ extremely rare interactions with the argon nuclei. The more nuclei, the greater the probability of an interaction taking place. Using argon will help better detect electron neutrinos specifically because when a neutrino hits an argon nucleus it emits an electron (resulting in a electron neutrino as opposed to either the tau or muon flavors).

Though the Long-Baseline Neutrino Experiment seeks to enhance the study of something invisible to our eyes, its construction “would make Fermilab the world headquarters of neutrino research,” said Strait. The LBNE and the installation of a new, more powerful proton beam (called Project X) would cement Fermilab’s future on a global scale for decades to come, according to Strait.