Fermilab Explores New Physics Frontier

May 14, 2009

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Researchers at Fermi National Accelerator Laboratory seem poised to answer some of the most basic questions in science. But now, the focus of high-energy physics is moving away from Chicago's western suburbs. Europe's Large Hadron Collider is expected to dwarf Fermi's collider into obsolescence. Fermilab now has to figure out how to keep up its prominence, its funding, its relevance. So scientists there are making a big pivot, training their sights on a new physics frontier.



Of all the people at Fermilab – cosmologists, Nobel laureates, John Plese may have the coolest job title: lab herdsman.

PLESE: Well that's the herd bull right there, lying down, getting ready to turn over and itch his back.

On a sunny spring morning, this herd of American bison is lolling in the grass. Plese, a muscled guy with a buffalo tattoo on his right shoulder, has been looking after them for about 20 years.

PLESE: They'll get up from this, and they'll wanna play. You see the babies. They'll start running around, just like you'd see puppies playing. Ha ha. They're funny sometimes.

The bison were brought in by the lab's founding director. They honor the site's prairie heritage, and they symbolize the lab's position at the energy frontier.

Fermilab's Tevatron machine has been the highest-energy particle collider in the world. It lets scientists smash particles together at such high energies that they blow up, and create new particles – which can then be studied. But the energy frontier is about to recede from view here. The European collider is expected to have seven times the Tevatron's energy. So Fermi has begun looking to a different horizon altogether, hoping to keep the frontier of discovery right here on the Illinois prairie.

Much of this lab's future, and maybe American preeminence in pure science, depends on one impossibly tiny particle.

RAMEIKA: A neutrino is as close to nothing as you cab get, and we'll still call it matter.

Gina Rameika runs a neutrino experiment here.

RAMEIKA: We know that they're created, they're all over, they're in nature, you're standing in them right now. There's 10 to the … many, many zeroes of neutrinos passing through your body right now, coming from the sun.

Neutrinos barely interact with matter at all. They're oblivious to gravity, and they're so light that scientists long thought they had no mass. But these particles are tied up with the reason everything – from galaxy clusters to American bison – is here today.

To peer into these mysteries, we put on hardhats and take an elevator down 330 feet below ground. Down below is a tunnel, bored out with mining equipment. Groundwater percolates through the bedrock. And keeping us company are untold zillions of neutrinos, beamed through the rock by a particle accelerator. About one in every thousand trillion will smack into the nucleus of an atom in a colossal detector here.

RAMEIKA: It's simply plates of iron interleaved with particle detectors that will be able to take a picture of particles as they go through.

This thing lays the groundwork for research at the intensity frontier, the next place Fermilab is hoping to make its mark. Instead of speeding up particles really fast, this work relies on cramming as many particles as possible into a beam.

Down the line, this may shed light on a puzzle dating to the first seconds of the universe. Scientists are pretty sure the Big Bang produced equal amounts of matter, and its opposite: antimatter. When matter and antimatter collide, they cancel each other out. If equal amounts collide, there should be nothing left. But here we are. Physicists call this CP violation.

RAMEIKA: You look for the origin of that in all the particles you study. And one of the places where we haven't been able to look yet is in neutrinos. So, it's that fundamental, that we actually have the possibility in the neutrino sector to get a glimpse at the very, very origin of CP violation.

For matter to win out over antimatter, something must have tipped the balance early on. Theoretical physicist Boris Kayser says that something may have been an extinct species of super-heavy neutrinos, and what they left behind.

KAYSER: The hypothesis is, when these heavy neutrinos decayed very early in the universe, they decayed into particles of matter, electrons, at a different rate than into particles of antimatter, positrons.

That means suddenly there would have been more matter than antimatter.

KAYSER: And that was the seed that began the asymmetry between matter and antimatter in the universe.

This is pretty lucky for us, says Kayser, considering what happens when matter and antimatter get together.

KAYSER: It is essential to our existence that there is almost no antimatter in the universe. If it were there, it would be annihilating us.

So the universe may owe its life to neutrinos. Understanding them could also be crucial to the survival of Fermilab.

ODDONE: It's really a vast sector that, unless we understand it, we're not going to be able to ever claim that we understand particle physics.

Lab director Pier Oddone hopes that sector will lead Fermilab back to the field's cutting edge. A proposed new accelerator would create, among other things, the world's most intense beam of neutrinos.

It's a more modest project than trying to build the next big atom-smasher, and it would mean ceding leadership, for now, on the energy frontier. It's a little like an aging runner pulling out of the sprint events, and looking to medal in the distance races instead. Oddone still wants to milk the Tevatron for a few more years – if he can convince the funders.

ODDONE: There is a big tension between getting on with the future, since we're going to shut this machine off, and running the machine so we can get to the punch line. I make the case that we need to do both.

Boris Kayser says those big machines have a natural lifecycle. So his timing is looking pretty good right now.

KAYSER: Now Fermilab is moving to the intensity frontier. For someone like myself who has been fascinated by neutrinos for a very long time, gee what good luck!

The neutrino used to be a second-fiddle player to the high-energy research. But if the money comes through, and the science proves out, the neutrino may soon get its chance to shine here. Boris Kayser couldn't be prouder.

KAYSER: When you look at the sun, what you imagine is that light is coming from the sun. What I immediately think of, and I am not making this up, is all those neutrinos are coming from the sun! ha ha! And you know, when the sun is obscured with all those clouds, I feel better for the fact that I know the neutrinos are still reaching me.

There may be cloudy days ahead for Fermilab. But scientists take some comfort in the promise of these elusive little particles.