Local scientists edge closer to their field of dreams

Finding Higgs boson would lead to new avenues of discovery

For people living in the western suburbs, catching a glimpse of the beginning of time is within an hour’s drive.

Researchers at both Argonne National Laboratory near Darien and Fermi National Accelerator Laboratory near Batavia have worked for years on identifying an elusive subatomic particle. Finding it will help advance scientific knowledge of how the universe began.

Physicists worldwide took notice July 4 when officials at CERN (the European Organization for Nuclear Research) in Switzerland announced they found what they believe to be the Higgs boson. Researchers at Fermilab had detected a similar discovery two days prior when poring over data from experiments done there.

“It would open a new window, having discovered the Higgs boson,” said Pier Oddone, Fermilab’s director.

“While scientists are being cautious before making any firm conclusions, most of the people involved believe it is likely that they have discovered the Higgs boson or a particle very similar to it,” said Don Lincoln, a Fermilab scientist. “We’re not sure, but I wouldn’t bet a lot of money against it.”

What was detected this year may be another key part of the puzzle that scientists have been piecing together in trying to understand the origins of the universe. The game of hide and seek has been going on for about 50 years.

 

Does this boson make me look fat?

James Proudfoot, a Higgs researcher at Argonne, said the subatomic particles that make up the universe and their interaction with each other are categorized in what is called a gauge theory. In its purest form, the gauge theory does not ascribe any mass to these elements, he said.

But some of these particles gained mass just after the Big Bang, and this process confounded scientists. Peter Higgs, a physicist and professor emeritus at the University of Edinburgh, is one of several researchers who in 1964 envisioned how this was accomplished.

There must be a field the particles interact with that gives them mass and initiates the process of forming atoms and creating matter, Higgs believed. To confirm the existence of this Higgs field, researchers have conducted experiments to find its associated boson.

A boson is one of the particles comprising the standard model, a theoretical construct of the elements that make up the universe and the forces that act upon them. The discovery of the Higgs boson would complete this model.

Particle accelerators like the Tevatron at Fermilab collide subatomic elements and examine what happens. This creates conditions similar to what the universe was like at the Big Bang.

The Tevatron began operating in the mid-1980s and ran until last year. Much of this work in particle physics is now done by the Large Hadron Collider at CERN.

“When the particles collide and there is a lot of energy concentrated in a very, very small space, ... elementary particles are produced in the interaction including particles that we no longer observe in nature because they have a very short lifetime,” said Luciano Ristori, a physicist at Fermilab. “So they were created at the beginning of time, at the Big Bang. But then they all decayed very rapidly, in less than a millionth of a billionth of a second. ... And so this way we can create these particles again and observe them, measure their mass, measure their lifetime, their properties and understand ... what actually went on when the universe was created.”

Both the Tevatron and the LHC use detectors to provide a clear picture of what happens when particles collide. Particles travel in opposite directions through circular tubes until they smash together.

Two detectors positioned alongside each other at Fermilab are called CDF and DZero. The beam of particles from the Tevatron passes through both detectors to record data from the collisions.

The denser this beam of particles can be made and the faster it can be sent, the higher the energy created at the point of impact. The Tevatron is nearly four miles in circumference while the LHC is more than 16 miles in circumference, giving the LHC the advantage in creating a higher-energy impact.

“So a particle collides, right? And in fact it’s the sub-elements of these particles that we believe are colliding,” Proudfoot said. “And they spit off a spray of other particles. ... And so what we do is we infer what happened in the interaction by measuring this spray of particles.”

In studying the effects of all these particle collisions, researchers have been able to reduce the region of mass where the Higgs boson can be detected. Scientists have now observed some unusual behavior that’s consistent with what they believe is this particle in the area that’s left.

 

Standing on the tiptoes of giants

Confirming whether what has been discovered is actually the Higgs boson will take months. And scientists don’t know if they’ll find one or multiple Higgs bosons.

“The simplest theory is that it’s one and the same. However, you could write down a theory that one Higgs boson does one thing and one Higgs boson does the other,” said Tom LeCompte, another Higgs researcher at Argonne. “We’re asking ourselves this question right now. Can we come up with a consistent story that it either takes more than one or it doesn’t? Right now, we just don’t have enough information; we can’t tell. In fact, the data is sitting right between those two possibilities right now.”

Scientists from both Argonne and Fermilab involved in the search for the Higgs boson have been analyzing data from two high-energy particle physics experiments being conducted at CERN. Researchers from Argonne have focused on the ATLAS project while Fermilab researchers have been involved with the CMS experiment.

While identifying the Higgs boson would answer one question, it would bring up dozens more. But each time scientists put in another piece of the puzzle, the whole picture becomes that much clearer.

“If you’re a kid and you’re trying to look at the top of a dresser, you can’t see it. You don’t know what’s up there. You stand on your toes and you can’t see,” Lincoln said. “But when you get to that magic height, you can all of a sudden see what’s on top of that dresser. And if we just get to a little higher energy, who knows what we will find when we stand on that little bit more tiptoes. And these are all the kinds of things we’re trying to do.”