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Higgs field prediction lands Nobel Prize in physics

By Andrew Grant and Gabriel Popkin

BIG BANG  This CMS collision event shows characteristics expected from the decay of the standard model Higgs boson to a pair of photons (dashed yellow lines and green towers). The prediction of the Higgs particle won scientists the Nobel Prize in physics.

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The prediction of the mass-bestowing Higgs field and the famous particle that goes with it has won the 2013 Nobel Prize in physics.

The Nobel committee selected Peter Higgs of the University of Edinburgh in Scotland and François Englert of the Université Libre de Bruxelles in Belgium, who in 1964 separately proposed the existence of a field that permeates the cosmos and gives mass to certain elementary particles. Confirmation of their theory came on July 4, 2012, when researchers at the world's most powerful particle accelerator, near Geneva, announced the discovery of the Higgs boson.

The Higgs boson was the final piece of the standard model of particle physics, which catalogs the universe's particles and forces and predicts how they interact with each other.

While the award comes just 15 months after the headline-grabbing experimental confirmation, it has been a long time coming for Englert, 80, and Higgs, 84. As young physicists in the early 1960s, they independently set out to tackle a perplexing problem. Particle physicists were discovering a zoo of subatomic particles and the intricacies of the forces acting on them, yet they could not explain why some particles have mass and others, like photons, do not.

Within two months of each other, the two physicists proposed the same solution in Physical Review Letters. They theorized the existence of a field that began exerting influence a split second after the Big Bang. Photons that carry the electromagnetic force were not affected by the field and so were massless. But particles of matter were slowed by the field and attained mass. Englert wrote a three-page paper with colleague Robert Brout, who died in 2011. Higgs' subsequent paper was a page-and-a-half long and explicitly predicted the Higgs boson, the particle that is essentially a knot in the field, providing a target for experimental physicists seeking to confirm the theory. A few months later, physicists Gerry Guralnik, Carl Hagen and Tom Kibble proposed the same field.

A sticky situation developed over the next several decades: Physicists began plugging the Higgs field into their equations and made the Higgs boson the cornerstone of the standard model, yet they had no proof that either existed. Without them, the otherwise successful standard model would fall apart.

The first detailed proposal to observe the Higgs boson experimentally came in 1986. The proposed Superconducting Super Collider in Texas would have done the job, but its funding was canceled by Congress in 1993, when the facility was only partially constructed. The Tevatron particle accelerator in Batavia, Ill., which operated from 1983 to 2011, didn't quite have the energy to find the particle.

The final tease came in 2008, when the $10 billion Large Hadron Collider, designed to have more than enough energy to find the Higgs, had to shut down for repairs just after it had been turned on. The machine came back to life in 2010, and the more than 6,000 Higgs hunters on the project began seeing little bumps in their data that suggested the existence of the particle. Finally, LHC researchers announced they had enough evidence to conclude that they had uncovered a new particle whose properties were consistent with the Higgs boson.

Since then, researchers have determined that the particle is indeed the Higgs boson predicted by the standard model. The particle looks and behaves exactly the way theory says it should, with the exception of a much lower-than-expected mass. Physicists hope to use that clue as a springboard to predict and observe new particles and forces. "The mass tells us that our standard model is incomplete," says Don Lincoln, a member of one of the LHC teams that made the discovery. "There must be undiscovered physics to correct this."

Although many prognosticators pegged the Higgs research as the front-runner for the Nobel, the committee took a full hour longer than expected before making the announcement. Nobel physics committee secretary Lars Bergström would not say why the committee, which decided on the prize on the morning of its announcement, needed the extra deliberation time. The discovery of the Higgs boson could still receive future recognition. "Every year is a new year," Bergström says. "Nominations that come in next year may well propose the experimentalists who actually made the discovery."

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