When particle physicists from around the world gathered in Melbourne, Victoria, Australia for the 36th International Conference on High Energy Physics last week, the atmosphere felt more appropriate for an excited crowd at a winning high school football team’s championship game than an academic conference.
That’s because scientists from the Switzerland-based European Organization for Nuclear Research, CERN, were expected to make a possibly game-changing announcement, based off the results from two main experiments at the Large Hadron Collider.
That announcement came on July 4 after 40 or so years of theorization and work, billions of dollars spent by various European countries, and the construction and implementation of the largest particle accelerator and collider in the world. Spokespeople Fabiola Gianotti and Joe Incandela (from the ATLAS and CMS experiments, respectively), smiles on their faces, told the world that they had made a breakthrough discovery: they had found evidence that a “Higgs-like” boson does in fact exist.
“This is indeed a new particle,” Incandela said. “We know it must be a boson and it’s the heaviest boson ever found.”
Gianotti told reporters at a joint CERN press conference that the experiment had gone faster than expected, and it was going very well.
“These last few weeks have been extremely intense,” she said. “I’m really amazed by everyone. Everybody was really focused.”
One of the eminent theorists responsible for the search for the boson and its namesake, Peter Higgs, was present for the announcement and made a brief statement at a seminar preceding the press conference.
“I would like to extend my congratulations (to the ATLAS and CMS experiment teams),” Higgs, who just turned 83 in May, said. “It is an incredible thing that it’s happened in my lifetime.”
Higgs and five other scientists theorized the existence of a particle field, which lent mass to other particles, around 1964, when they published a series of papers called the “PRL symmetry breaking papers.”
In Higgs’ paper, titled “Broken Symmetries and the Masses of Gauge Bosons,” he wrote that “The purpose of this present note is to report that, as a consequence of this coupling, the spin-one quanta of some of the gauge fields acquire mass; the longitudinal degrees of freedom of these particles (which would be absent if their mass were zero) gov over into the Goldstone bosons when the coupling tends to zero.”
In layman’s terms? Fundamental particles like quarks, for example, gain mass thanks to the existence of a Higgs boson field. If it didn’t exist, then there should be no reason for a quark to have a mass.
This theory rose to some prominence in the early 1970s, when Nobel prize-winning theoretical physicist Stephen Weinberg utilized the Higgs mechanism in his contribution to the unification of electromagnetic and weak force interactions. This unification, in turn, contributes to the current accepted model of understanding in particle physics, the Standard Model.
“The Higgs field is the only way for particles to acquire mass,” UCO physics professor Weldon J. Wilson said. “There hasn’t been another plausible theory for why fundamental particles have mass.”
The main problem (until now) has been: how can physicists prove that the Higgs field exists beyond a mathematical theory?
Several particle accelerators, including the Large Hadron Collider (LHC) in Geneva, Switzerland, Tevatron in Chicago and the Superconducting Super Collider (SSC) outside of Dallas, have either been proposed or built for the purpose of finding the field. The SSC was slated to be the largest particle collider in the world, with a proposed 40TeV collision energy—three times higher than the current energy used by the LHC. Its budget was scrapped in 1993, effectively canceling the project.
The LHC, on the other hand, was funded by a consortium of nations and therefore withstood the hefty price tag of $5 billion. Construction on the collider was started in 2000, in the 27-kilometer-long cavern where its predecessor, the Large Electron-Positron Collider, sat. The LHC began full operation in November 2009.
According to Incandela, approximately 500 trillion collisions have been produced for the purposes of finding the Higgs—and positive results have only numbered in the tens of thousands. “(500 trillion) is enough to where, if it were sand, it would fill an Olympic sized swimming pool,” he said.
Despite that massive amount of data, and a certainty of over five sigma (99.9767 percent), the spokespeople were only cautiously optimistic.
“We have reached a milestone in our understanding of nature. The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will peer down the new particle’s properties, and is likely to shed a light on other mysteries of our universe,” CERN Director General Rolf Heuer said. “As a layman, I would say we have it. As a scientist, I have to ask, what, exactly, have we found?”