Peter Higgs and François Englert shared the Nobel Prize in physics for independently proposing a particle, now known as the Higgs boson, that confers mass to all other particles and whose recent discovery stands as one of the seminal moments of modern science.
Nearly a half-century after predicting the existence of the particle, the pair's work was confirmed last year, in a nail-biting experiment undertaken at the atom-smashing machine built by the European particle physics laboratory at CERN in Switzerland. That July day, in a packed hall in Geneva, Drs. Higgs and Englert met for the first time.
After further analysis, physicists at the Geneva laboratory said earlier this year they are confident that the particle they had discovered was in fact the one Mr. Higgs and his colleagues had predicted.
Though widely expected, the latest Nobel award is also a controversial one, partly because several other scientistsand CERN itselfcan claim significant credit for work done on the boson. A Nobel Prize can be shared by a maximum of three people and isn't granted posthumously.
Dr. Englert, a Belgian who is now 80 years old, published his landmark 1964 paper with colleague Robert Brout, who died in 2011. Other strong contenders were three scientists, Carl Hagen of the University of Rochester, Tom Kibble of Imperial College and Gerald Guralnik of Brown University, who published a very similar theory just one month after Dr. Higgs of the U.K. published his paper, which affixed his name to the fabled particle for posterity.
"I'd be lying if I said it doesn't sting a little" not to share in the prize, said Dr. Guralnik in a phone interview. "No matter what, [the Nobel committee] had a difficult time" in choosing the winners.
But, he added, "we are amazed and delighted that our mathematical exercise turned out to play a huge part in describing how nature works."
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In a statement, Dr. Higgs, of the University of Edinburgh, congratulated "all those who have contributed to the discovery of this new particle."
The Higgs boson explains a big puzzle about matter concerning why some objects in the universe such as the quark, a constituent of protons, possess mass, while others, such as the photon, a constituent of light, have only energy and zip around the universe unhindered.
Until this enigma was resolved, physicists couldn't properly explain why many things in the universe exist, from stars and planets to germs and people.
Dr. Higgs and others explained away the problem by proposing a ghostlike field that pervades the universespace, after all, is already filled with other invisible fields, such as the gravitational field and electromagnetic field.
The scientists' notion was that particles acquire mass only in contact with this field, which would become known as the Higgs field. How much mass they acquire depends on the type of particles they are. Some, like the photon, seem to ignore the field and don't acquire mass at all.
By contrast, electrons interact with the field. If the field were to disappear, the suddenly massless electrons would zoom away at the speed of lightand all matter would collapse.
"The Higgs field is always there," said Dr. Guralnik, who is 77. "It slows down the particles and induces a mass to them."
The Higgs boson and its associated field neatly filled a potentially embarrassing hole in one of the most successful theories of physics, known as the standard model. But it was only a theory. It took half a century for the physicists' bold theoretical leap to be confirmed by experimental science.
Last year, hundreds of scientists assembled at CERN and others tuned in to a live webcast to hear a report on the latest data from the Large Hadron Collider. The quest for the elusive Higgs had involved some 6,000 scientists, cost millions of dollars and required billions of particle collisions.
"I think we have it," said Rolf-Dieter Heur, director general of CERN.
Dr. Higgs, now 84, received a round of applause when he entered the auditorium, and shed a tear on hearing the news.
"The miracle of the standard model is that it works so well," said Dr. Guralnik. "But we have many, many open questions, such as [the mystery] of how gravitational interactions occur."
Dr. Higgs, for his part, was glad his main finding had been so concretely and dramatically confirmed. "It is an incredible thing that it has happened in my lifetime," he said.
The Nobel Prize in physics is seen as the most prestigious award of its kind, and comes with an 8 million Swedish kronor ($1.25 million) cash award. The winner is appointed by the Royal Swedish Academy of Sciences, after a process in which thousands of scientists world-wide are invited to name contenders.Niclas Rolander in Stockholm contributed to this article.
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