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University of Oregon physicists help discover elusive particle

Published: Sunday, July 08, 2012, 9:00 PM     Updated: Monday, July 09, 2012, 5:44 AM
University of Oregon physics faculty and graduate students played a big role in last week's discovery of an elemental building block of the universe: a particle called the Higgs boson.

The Higgs boson, called the "God particle" by some (although many physicists revile the term), was predicted by a theory called the Standard Model, which explains the behavior of atoms. Without the Higgs boson, the Standard Model couldn't explain why matter has mass.

Although physicists expected the particle to exist, nobody had ever observed it -- until now. That made it one of physics' most anticipated discoveries.
What's a particle accelerator? An atomic racetrack where a building block of atoms called protons are accelerated to nearly the speed of light by powerful magnets. When two protons collide, they break down into even tinier particles that physicists want to study.
How powerful is it? At its peak, each pulse of the particle beam in the Large Hadron Collider, the particle accelerator used by the University of Oregon team, releases energy equal to about 310 sticks of dynamite.
Any uses outside of physics research? Particle accelerators are key for making the radiation treatments used in hospitals for cancer patients and for manufacturing the shrink-wrap around turkeys in the grocery store.
What's a Higgs boson? A boson (named for Indian physicist Satyendra Nath Bose) is a type of subatomic particle that spins on an axis like a globe in a different pattern than other subatomic particles. The Higgs boson (named for British physicist Peter Higgs) is a type of boson that, in short, explains why particles have mass. Particles get their mass from an invisible field called the Higgs field, but the theory that explains the existence of the Higgs field requires the Higgs boson. Without one, the other doesn't fit the theory.



The elusive particle was created by the Large Hadron Collider, a particle accelerator in Geneva, Switzerland, run by an international team that includes several UO faculty and graduate students.

HIGGS_BOSON_20251551.JPGView full sizeThe University of Oregon's Jacob Searcy, a physics graduate student, sits in the ATLAS control room at the Large Hadron Collider in Switzerland. Searcy is part of the UO group working on the project responsible for the discovery of the Higgs boson.

The Large Hadron Collider shoots pieces of atoms called protons at each other at nearly the speed of light. By carefully steering them around an atomic racetrack, physicists can create some of the highest-speed collisions allowable by the laws of physics. Much like how a car crash scatters broken auto parts throughout an intersection, so too can a proton crash scatter broken proton parts.

But the parts are too small to see even with the most sensitive microscope, so scientists built another type of detector called ATLAS, which is capable of measuring the pieces' energy signatures.

UO professor Jim Brau helped design this system -- and is already working on its successor.

The electromagnetic stoplight that sends protons on their collision course allows so many to happen -- millions of collisions each second -- that it would be impossible to store a record of each one. The ATLAS team predicts that they could fill 100,000 CDs every second if such a task was feasible.

Instead, they only save collisions most likely to reveal something new. That's where David Strom, another UO professor, comes in. He is the coordinator for the trigger, which decides whether or not to save each event.

This is a delicate task, said Searcy. "If you do it wrong, it's like you never did the experiment in the first place."

For scientists to accurately measure the number of collisions occurring, they need to know how many particles the beam is made of. Associate professor Eric Torrence plays a key role in determining this value.

Searcy's doctoral research project was performed using the ATLAS detector. He noted that in return for the data returned by the multi-billion dollar machine, he worked as a shift leader to keep the machine running 24 hours a day. Luckily, he said, there were no major breakdowns on his watch.

The Higgs boson's discovery is a key achievement in physicists' understanding of the universe. "As an Oregonian, I think it's amazing to be part of this effort," said Searcy, who grew up in Albuquerque, NM. "We are probing the universe at a level of detail that was never possible before."

The next step is to more thoroughly determine the Higgs boson's properties. Although scientists are confident the particle exists, they haven't yet confirmed that it perfectly follows the Standard Model's predictions.

If it behaves in unexpected ways, the Higgs boson could lead to new developments in theoretical physics. "This is the start of a new generation. I think it's very exciting," concluded Searcy.

-- Ian Campbell
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