U scientists help find Higgs boson particle

The ‘historical’ discovery could explain how the universe acquires mass.

by Rebecca Harrington

An international collaboration that includes 29 University of Minnesota scientists announced the discovery of a new particle last week that could explain unknown aspects of the universe.

The Higgs boson, which scientists theorize gives every particle mass, was observed at the world’s largest particle accelerator, the Large Hadron Collider.

They were able to observe the Higgs boson because within the LHC, protons travel at nearly the speed of light and smash into each other — reaching energies comparable to what scientists think occurred during the Big Bang.

These energies are measured by the LHC’s calorimeter, which University physics professor Roger Rusack helped design. He also led the group that operated it from 2009-10.

Since 1993, the University has been represented in the global group of nearly 4,300 people who discovered the particle, the European Organization for Nuclear Research, or CERN, which is located in Switzerland.

Upon returning to the University, Rusack has been teaching, assisting graduate students and doctoral candidates and managing grants for the University group. The technology CERN uses allows him to continue to participate in the effort from Minnesota. After all, CERN scientist Tim Berners-Lee invented the World Wide Web in 1989 to help CERN scientists communicate with one another.

Higgs history

In the 1960s, scientists theorized the existence of an energy field that interacts with every particle. The more particles interact with the field, the greater mass they gain.

Peter Higgs wrote a paper proposing that the particle within this energy field could be observed because it would also interact with itself like it interacts with every other particle.

Thus, the particle became known as the Higgs boson — its surname coming from Indian scientist Satyendra Nath Bose, who defined “bosons” as a kind of particle, according to the Associated Press.

Scientists have been searching for the Higgs boson ever since. Because it decays instantaneously into other particles, the researchers at CERN were actually observing its decay products — smaller particles like electrons and quarks.

Rusack said the discovery is significant because two separate experiments observed the particle’s decay products with a “five sigma probability,” meaning a 99.99995 percent chance the results could be duplicated.

He said CERN also has safeguards to prevent data manipulation during experiments.

“In these types of things, it’s very easy to kid yourself into thinking you’ve found something,” Rusack said.

Although the discovery was a surprise to the world, doctoral candidate Kevin Klapoetke said, CERN scientists knew about it in January.

“It’s not so much of a surprise that something we began to see is finally taking shape and we can confidently say is a Higgs-like particle,” he said.

Klapoetke called it “Higgs-like” because researchers don’t yet know if the particle is exactly what scientists predicted nearly 50 years ago. Rusack said researchers will perform precision measurements on the rate of decay to see if it’s the Higgs boson as predicted or something different.

Thousands of opinions

Rusack said the thousands of people working on the CERN project get along well because they use the “universal language” of science.

“We’re all there because we’re excited about the physics,” he said. “We have a common understanding of the application of the scientific method.”

But Klapoetke said the massive partnership isn’t always easy.

“You’re working with a lot of people so you have unlimited possibilities of problems,” he said.

The contributions students like him have made to the CERN project include programming the software the machine uses to detect particles.

He said he currently has a program that works but getting it accepted into the standard process has not been easy because there is no clear, written explanation of how things should be done.

“In the end, yes, we want it to be uniform and simple so that when you go looking for it it’s not a pain in the butt,” Klapoetke said. “But to get things to that state is a huge, troublesome thing.”

When things start to work, though, he said it’s satisfying. Klapoetke said he also enjoys the recognition when something he designed makes it into a scientific publication.

With nearly 4,300 contributors, the authorship of CERN publications is extensive.

Klapoetke said in a paper like the one researchers will publish on the Higgs boson discovery, every name is included.

“You can’t ever pretend you did it yourself,” he said.

Peter Hansen, who will start graduate school at the University in the fall, started working on the CERN project in May.

Hansen said he was glad to join the group amid this discovery.

“It’s also a pretty historical event,” he said. “It’s one of those things that you know will be known for a long time.”

Although the discovery has earned international attention, CERN researchers are far from finished.

On the Monday following the Higgs boson announcement, Rusack logged in to his CERN account and pulled up a screen that showed what the LHC was doing at that moment, more than 4,400 miles away.

Then, he looked at the meetings for that day. This week, most are about the Higgs boson and the further tests CERN scientists are going to do on the particle.

Rusack found a meeting of interest and joined it via video conference. He said meetings are a big part of life with CERN no matter where he is in the world.

“When you have that many people,” he said, “you have to have that many meetings.”