UNL team assists hunt for Higgs boson

Image from inside the Large Hadron Collider.
Image from inside the Large Hadron Collider.

Physicists at CERN laboratory in Switzerland announced July 4 that they have observed a new particle whose characteristics match the long-theorized Higgs boson particle, the central part of a hypothesis that could peel away the very fabric of the universe and influence the understanding of all matter.

For UNL's experimental high-energy physics team, the announcement was a significant moment in the group’s decades-long collaboration in the hunt for the elusive subatomic particle, which has been dubbed by some observers as the “God Particle.”

The Higgs boson could explain why some particles have mass and others do not, said Gregory Snow, professor of physics and astronomy. CERN’s atom-smashing Large Hadron Collider has been generating high-energy collisions of protons in its search for the final piece of the theoretical framework, which is known as the Standard Model of particles and forces.

Without the Higgs boson, however, the Standard Model cannot explain how most of these particles acquire their mass, a key ingredient in the formation of the universe.

“We now have firm, statistically significant evidence that we’ve observed a new particle – a particle that has a mass that is consistent with what we have expected to see with the Higgs boson,” said Snow, founding member of UNL’s experimental high-energy physics team that has aided in the Higgs search since 1993.

The results announced are labeled preliminary and are based on data collected in 2011 and 2012, with the 2012 data still under analysis. A more complete picture of the announced observations will emerge later this year after the Large Hadron Collider provides the experiments with more data. The new particle is in the mass region around 125-126 GeV, or gigaelectronvolts. Publication of the analyses shown today is expected around the end of July, officials said.

For years, two project teams at CERN have utilized two separate, massive detectors in an attempt to provide independent confirmation of one another’s work. One project is known as CMS, the other ATLAS.

In addition to helping develop portions of the CMS project’s particle detector, UNL’s physics team has contributed to different aspects of data analysis with CMS as the pursuit of the particle has narrowed.

“What we can’t say with 100 percent certainty yet is that this new particle we’re observing is, indeed, the Higgs boson particle,” Snow said. “We’ll need some additional data and data analysis to say that with certainty – but all the arrows are certainly pointing in the right direction.”

UNL’s experimental high-energy physics team also includes faculty members Ken Bloom, Dan Claes, Aaron Dominguez and Ilya Kravchenko, and several other researchers working in Lincoln, at CERN in Switzerland and at the Fermi National Accelerator Laboratory in Batavia, Ill.

Snow said the UNL team is one of the larger U.S.-based groups participating in the CMS project. The vast majority of U.S. scientists participate in the LHC experiments from their home institutions, remotely accessing and analyzing the data through high-capacity networks and grid computing. UNL is one of seven CMS Tier-2 sites in the United States in the Worldwide LHC Computing Grid, which combines the computing power of more than 140 independent computer centers in 34 countries to analyze results from the Large Hadron Collider’s experiments.

Bloom is the Tier-2 coordinator for the United States in the CMS experiment and is co-primary investigator on the UNL part of the project with Dominguez and computer scientist David Swanson, director of UNL’s Research Computing Facility. Bloom is also deputy program manager for U.S. CMS software and computing.

More than 1,700 scientists, engineers and graduate students from the United States collaborate on the experiments at the Large Hadron Collider, most of them on the CMS and ATLAS experiments, through funding by the Department of Energy Office of Science and the National Science Foundation.

Brookhaven National Laboratory serves as the U.S. base for participation for the ATLAS experiment, while Fermilab serves as the U.S. base for participation in the CMS experiment.

In many ways, Claes said, this announcement means the work has just begun. Scientists will need to observe and precisely measure the particle behaving consistently in the manner in which it has been theorized. And its discovery would represent only the first step into a new realm of understanding of the world around us.

“While the discovery of the Higgs may appear to close the list of fundamental particles required by the existing theory, the truth is that the theory still has some mathematically inconsistent pieces that suggest there is actually more to be discovered,” Claes said. “There is still a lot to explore.”

- Steve Smith, University Communications