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The Particle Blasting Experiment That's Trying to Determine Why Matter Exists

By bombarding a 14,000-ton plastic structure with cosmic rays, from 500 miles away.

by Jason Koebler
Oct 7 2014, 10:00am

Image: Fermilab

Yesterday, scientists at America's most advanced particle physics laboratory began shooting cosmic rays through the Earth at a neutrino detector more than 500 miles away in what's being billed as an attempt to figure out why we exist (in a strictly particle physics kind of way).

Neutrinos are believed to be the most common particles in the universe, but, because they move so fast, are so light, and have no charge, they're paradoxically some of the hardest to detect. It's estimated that every second trillions of neutrinos pass through our bodies—like, it's happening right now.

Fermilab's NOvA experiment is an attempt to explain how, exactly, neutrinos switch between their three "flavors" (there are muon neutrinos, electron neutrinos, and tau neutrinos, each with different properties—but neutrinos can "oscillate" between the three types).

Beyond that, the researchers hope to answer a couple of other questions that could fundamentally explain why we exist: It's theorized that the big bang created equal amounts of antimatter and regular matter, but, for some reason, there's more matter today than there is antimatter (because when the two meet, they destroy each other). That's why we're here. 

Because they have no charge, it's thought that perhaps antineutrinos and neutrinos behave slightly differently than each other—which, if true, would suggest that maybe matter and antimatter aren't exactly mirror opposites either. That'd explain a lot, or at least open up a whole lot more questions and lines of inquiry into the nature of whether matter and antimatter have these same fundamental differences.

So, it's some pretty heavy stuff. How the heck do you go about testing this? Well, by constantly bombarding the largest freestanding plastic structure with tens of thousands of billions neutrinos per second, of course. That structure weighs 14,000 tons and is 60 meters long, 16 meters wide, and 16 meters tall, by the way.

As Fermilab explains, cosmic rays continually bombard the structure in Minnesota, having been sent from Fermilab back in Illinois. Here's how that works:

"Scientists create the NuMI neutrino beam by firing protons from Fermilab's Main Injector into a graphite target resembling a long roll of quarters. Many different types of fundamental particles come out of the collision between the protons and the target, including pions, which are charged particles. Physicists use magnets to steer the pions in the direction they want the neutrinos to travel. The pions eventually decay into muons and muon neutrinos, which continue on the same path the pions were traveling.

The neutrino beam is aimed downward at a 3.3 ° angle. Although the beam starts out 150 feet below ground at Fermilab, it will pass as much as six miles below the surface as it travels toward Ash River, [Minnesota]."

As I mentioned, detecting neutrinos is really hard, because they rarely interact with anything (that's why they can be sent directly through the Earth), but if you know enough about the neutrinos, you can do it, Fermilab scientists say.

The neutrinos will be sent from Fermilab, just outside Chicago, to the Canadian border in Ash River, Minnesota. The trip will take 3 milliseconds. Image: Fermilab

"Scientists do know three things about neutrinos coming from Fermilab: The direction they are coming from, their energy, and the exact time each pulse of neutrinos should arrive," the lab said in a video explaining the experiment.

Because scientists have all of that information, and aren't just randomly trying to detect neutrinos that come from, say, the sun or radioactive decay, they'll be able to detect and analyze rare neutrino interactions.

They say that a neutrino interaction will look, to them, something like this:

Image: Fermilab

"The detector never sees neutrinos, but it does see the telltale traces they leave behind when they collide with other particles," the lab said.

And, well, it's already happened. The lab says it has already detected neutrino interactions with regular matter. The experiment begins.