Scientists at UC Berkeley weren't just smiling Friday – they were beaming over the recently announced discovery of a long-sought particle called the "Higgs boson" and the role that UC Berkeley played in making it possible.
Dozens had to be turned away from a packed campus auditorium where a panel of physicists described the mysterious sub-atomic particle whose existence has been sought for half a century.
The apparent discovery of the mysterious particle at the Large Hadron Collider in Europe, announced July 4 in Geneva, electrified the world of science, which hailed it as a major breakthrough in confirming the Standard Model, the leading modern theory about the fundamental nature of the universe. Comparisons are being drawn to the discovery of DNA.
"We physicists these days don't often get the chance to be rock stars," UC Berkeley Chancellor Robert Birgeneau, a physicist himself, said with evident enthusiasm in introductory remarks. "We're all really quite excited about it."
And though the physicists at the gathering acknowledged that they weren't sure precisely what kind of particle the Higgs boson is, they agreed that it's very important.
"If it weren't for the Higgs mechanism," Birgeneau said, "... then none of us would be here because none of us would have mass. We'd all be like light particles."
The particle supports the theory of Peter Higgs, a University of Edinburgh professor who argued that the universe consists not of vast stretches of empty vacuum but is filled with a field – now called the Higgs field – that permeates and shapes all the variety of existence. Some have compared finding the Higgs boson to finding a tiny chip of that mysterious field.
In his role as moderator, UC Berkeley's physical sciences dean, Mark Richards, noted Berkeley's roles leading up to the discovery, both historical and contemporary. Belonging to the latter were panelists Beate Heinemann and Marjorie Shapiro, who are UC Berkeley physics professors and members of one of the two teams that independently produced the Higgs boson findings at the Large Hadron Collider, which is run by the European Organization for Nuclear Research (CERN).
But long long before Higgs produced the 1964 theory that bears his name, Berkeley was laying the foundation for fundamental discoveries in particle physics, Richards said.
"The Berkeley physics department was the birthplace of big science, starting with the table top-sized cyclotron that Ernest Lawrence developed in LeConte Hall (in 1939), which eventually morphed into the 184-inch cyclotron in the big building on the hill (at what is now known at the Lawrence Berkeley National Laboratory)," Richards said.
He traced the continuing growth of particle physics and particle accelerators to the Bevatron at the Lawrence Berkeley lab, the SLAC accelerator at Stanford, Fermilab near Chicago and most recently the $10-billion Large Hadron Collider, whose diameter is about equal to the length of the Bay Bridge.
"It's a legacy that truly began here," Richards said.
The Friday event was organized because of the major significance of the new findings, Richards said.
"This is a moment where I think we can all feel very, very proud to be part of the human race," he said. "And that's why we're having this symposium. We want to share these discoveries with you."
When it came to describing exactly what was found, however, the physicists offered somewhat differing interpretations, while several prefaced their remarks with acknowledgements that the findings remain preliminary.
Heinemann referred to the particle found by her team as "a Higgs-like boson," and UC Berkeley theoretical physicist Lawrence Hall categorized the Higgs boson as a new type of particle, creating a third class of particles beyond the two acknowledged categories of elementary particles: matter particles like electrons and force particles like photons.
However, Hall added, the nature of the newly found object remains somewhat mysterious. "Is this Higgs an elementary point-like particle, or is it a big fluffy thing made up of something else?" he asked.
"It's clear that we found a new particle," said Louise Skinnari, a UC Berkeley Ph.D. student and member of the Atlas boson-discovering team that includes Heinemann and Shapiro. "What I find most exciting is really determining whether or not this is consistent with the Standard Model or it's an indication of other new physics."
Others raised the possibility that there could be more Higgs particles yet to be found.
"We might be looking for five Higgs-like particles," Richards said.
What scientists do know is that a large detector-machince – the 7,000-ton Atlas detector located where protons are smashed into each other along the 16.5-mile circular track – found enough evidence of the new particle that they believe there's virtual certainty of its existence.
The odds of the results being produced by chance are extremely small, only one in 3.5 million, Heinemann said. That would be like throwing eight dice and having them all be sixes, she said.
Still, the Higgs boson is not easy to track, nor does it decay in predictable ways. Sometimes it breaks up into two photos, other times into four electrons or muons, and in the vast majority of times, it's believed to decay in forms that scientists are still seeking to observe, Heinemann said.
Of the 800 trillion proton collisions observed in the Atlas experiment, the Higgs boson was detected in about 200 collisions, Heinemann said. The other team, CMS, reported an almost identical rate of detection in its 800 trillion collisions, Heinemann said.
The Large Hadron Collider, which lies under the French-Swiss border near Mont Blanc, has been running on only half energy, and when it ramps up to full force in 2015, scientists hope to learn more about the Higgs boson and also about other mysteries of the universe, particularly dark matter, the Cal physicists said.
Members of the audience seemed pleased with the presentation. Anne Baranger, campus director of undergrade chemistry, said she came away with a a better, though not perfect, understanding of the Higgs' boson. "It was really inspiring," she said.
Meixia Zhang, a graduate student in economics at Princeton, said she too came away with a clearer picture. "This is a third type of particle," she said. "... It has no mass – that's my feeling."
A video of the panel presentation is expected to be posted on the Cal physics department Web site early next week, campus officials said.
Meanwhile, those curious to know more about the Higgs boson might enjoy a New York Times article published the day of the discovery announcement, "What in the World Is a Higgs Boson?"