Higgs boson rocks the physics world

Pitt, CMU scientists celebrate 'milestone' in their own ways

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When the European Organization for Nuclear Research -- known as CERN -- announced the historic discovery of the subatomic "God particle" or "Higgs boson," University of Pittsburgh physicist Joe Boudreau was at the Center for Particle Physics in Marseilles, France, which had no champagne available because they did not realize how dramatic the announcement would be. Afterward, the center rolled out sparkling wine.

At the same moment, Carnegie Mellon University physicist Manfred Paulini was planted in front of his home computer at 3 a.m. to catch the action on streaming video. Both physicists knew the announcement would be exciting. Hearing that data were sufficient to provide nearly irrefutable proof of the particle's existence was surprising to most physicists. First predicted to exist in 1964, the Higgs boson provides mass to other particles and completes the standard model of particle physics, which explains the physics of subatomic particles.

So the grand announcement was important not only to their professional lives but to science and history.

"We have reached a milestone in our understanding of nature," CERN director general Rolf Heuer stated at the time. "The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle's properties, and is likely to shed light on other mysteries of our universe."

Mr. Boudreau and Mr. Paulini along with scientists worldwide celebrated the announcement, including 300 people who crammed into a conference room at the Fermi National Accelerator Laboratory near Chicago, with another room for crowd overflow for the announcement. Because the Fermilab is a government facility, the crowd celebrated with nonalcoholic champagne. Hundreds more watched the announcement at the world's largest particle physics conference in Melbourne, Australia.

Mr. Paulini, who has a doctoral degree in physics, didn't raise a glass of champagne to celebrate the breakthrough because "it was too early in the morning for alcohol," he said. "But this was a historical moment in particle physics -- the thing people have been awaiting for 30 years."

Discovery of the Higgs boson was one key reason for construction of CERN's Large Hadron Collider, whose particle accelerator, with its 17-mile circumference, straddles the Swiss and French border near Geneva. The world's largest and most powerful particle accelerator sends particle beams in opposite directions before colliding them. Equipment used in these experiments -- which Mr. Paulini and Mr. Boudreau helped to develop -- measure energy, mass and other properties to identify particles released in the collision.

The announcement last Wednesday put an end to, or at least a damper on, the competition among the two teams of physicists involved in developing the collider's two general-purpose subatomic particle detectors.

Mr. Paulini and his colleagues at Carnegie Mellon have worked nearly a decade on the Compact Muon Solenoid, or CMS, Experiment. Mr. Boudreau, a doctor of physics and key member of the Pitt team since 2003, developed software for the ATLAS Experiment and worked on its electromagnetic calorimeter, a device that measures energy that particles deposit.

There was competition between the teams, each involving thousands of scientists worldwide, over which one would first or more definitively detect the Higgs boson. That proved to be a tie.

Mr. Paulini said he'll focus on dark matter, another yet-to-be proven particle necessary to explain the gravitational forces of the entire universe.

Mr. Boudreau said he's happy both experiments had equally strong evidence of the Higgs boson and nearly identical high probabilities of accuracy. "It's absolutely beautiful to have confirmation from the other experiment," he said.

He's focusing his attention on the top quark, the only particle heavier than the Higgs boson, with the collider now providing a much larger data sample that allows more detailed study of its properties. Currently there's little known about the top quark. Physicists, who now know the mass of the Higgs particle, can focus on what particles it decays into among other properties and whether other variants of the Higgs particle exist.

"The announcement was greeted with applause that interrupted the presentation several times," Mr. Boudreau said. "I didn't think you'd ever see that in physics."

Since the announcement, most conversations with colleagues have involved admiration for what happened and its meaning to them.

"Finally you can say the era of looking for Higgs -- the entire time I've been in the field -- is over, and the era of doing physics with the Higgs is getting started," he said.

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