Another chapter has unfolded in the dramatic saga of the Higgs boson. On the morning of October 8, 2013, the Swedish Academy of Science made an announcement that had been widely anticipated by the blogosphere: Francois Englert and Peter Higgs shared the 2013 Nobel Prize for physics for the prediction of a new physics mechanism to which Higgs (unwillingly) lent his name.
Event recorded with the CMS detector. Image credit: CERN
The Standard Model of particle physics is a stunningly successful theory that describes the matter of the universe. It was developed in the 1960s and has been extensively validated in the intervening decades. However, the theory had one striking weakness. It did not explain why the smallest and most fundamental particles had mass, instead of being massless, which seemed to be a more natural state of affairs.
In 1964, Belgian physicists Robert Brout and Francois Englert published a paper describing a way to modify a class of so-called Yang-Mills theories. By adding a new field of energy to the existing theories, they found, they could give subatomic particles mass.
British physicist Peter Higgs independently developed the idea and his treatment was published a couple of weeks later. A third treatment of the problem by the American physicists Gerald Guralnik, Carl Hagen, and Tom Kibble appeared shortly thereafter. All three papers were named Milestone Papers by the American Physical Society in its 50th anniversary issue. A fourth paper, written by Peter Higgs, made the crucial observation that if this modification was true, it predicted a new particle. Over the intervening years, the energy field has come to be called the Higgs field and the predicted particle the Higgs boson.
While the ideas described in these papers from 1964 were possible explanations for the origins of the mass of fundamental particles, the ideas could have been wrong. In order to test the theory, scientists began a search for the Higgs boson.
On July 4, 2012, after nearly 50 years of searching, researchers using the Large Hadron Collider (LHC) at the CERN laboratory in Europe announced that they had found a new particle that was “consistent with being” a Higgs boson. In science, the term “consistent with being” has a technical meaning. It means that some of the predicted properties had been tested and verified but not all. It also means that no observations disagreed with the theory. By way of an analogy, if scientists had discovered a fruit that was consistent with being an apple, they might have touched and looked at the fruit and confirmed that it was apple-like, but they had not smelled or tasted it yet. Because of these residual uncertainties, awarding a Nobel Prize for the successful prediction of the Higgs boson in 2012 would have been premature.
In March of 2013, researchers updated their results, using two and a half times as much data as they used in July of 2012. With the extra data and more refined analysis techniques, the scientists were able to confirm that the newly-discovered particles had even more properties that were identical to those the Higgs boson was predicted to have. The case supporting the Higgs discovery was firming up.
There remains some possibility that the newly-discovered-particle is not the Higgs boson. For instance, the theories of 1964 predicted that a single variety of Higgs boson exists. Given that scientists have found only one variety, this is great news for the prediction. However it could be that there are other varieties of Higgs bosons that have not yet been discovered. Being absolutely sure will require more data taken at the LHC when it resumes operations in 2015.
So why award the Nobel Prize before this additional confirmation? First, the observed particle has many properties that are identical to the predictions of 1964. Those predictions seem to be part of the story. Second, time is a real concern. The prize cannot be awarded posthumously, and both Higgs and Englert are in their 80s. (Brout died in 2011.)
Thanks to the near-synchronicity of the milestone Higgs papers, narrowing the field of Nobel candidates must have been difficult. While the details of the selection process are private, it appears that the Swedish Academy of Science acknowledged that Englert and Brout got there first, while Higgs was the first to associate the new field with a particle. The decision was no doubt a difficult one, but is consistent with how the prize has been awarded in the past.
Our ongoing study of the rules that govern the universe is not complete with the observation of the Higgs boson, but the discovery is a tremendous step forward. The 2013 physics Nobel Prize is an affirmation of the importance of those ideas, first conceived of nearly half a century ago.
Author's suggestions for further reading
The Quantum Frontier: The Large Hadron Collider
Author Don Lincoln's look inside the LHC and the physics it explores.
Massive: the Missing Particle that Sparked the Greatest Hunt in Science
Science writer Ian Sample's examination of the quest for the Higgs.
Higgs: The Invention and Discovery of the God Particle
Science writer Jim Baggott on the history and implications of the Higgs discovery.
The Particle at the End of the Universe
Physicist Sean Carroll goes behind the scenes at the LHC to explore the story of the search for the Higgs.
Physicists are on the brink of a breakthrough discovery: They may have finally cornered the Higgs boson, the subatomic particle hypothesized to give mass to all the stuff in the universe. But should we really be calling this particle the “Higgs”?
A computer simulation of a detection of the Higgs boson. Or is that the ABEGHHK’tH boson? Credit: David Parker/Photo Researchers, Inc.
Peter Higgs, it turns out, wasn’t the only one to come up with the idea of a new field (the Higgs field) that endows particles with mass. In fact, he wasn’t even the first to publish the theory. That distinction goes to Robert Brout and Francois Englert at the Free University in Brussels, who wrote up the idea in August 1964. Higgs was close on their heels with his own paper in October of the same year. Just a few weeks later, Dick Hagen, Gerald Guralnik, and Tom Kibble published their take on what would come to be known as the Higgs field and Higgs boson.
This wasn’t plagiarism: It was a kind of synchronicity that is the norm in science, says MIT science historian David Kaiser. In fact, independent research groups simultaneously arrive at similar breakthroughs so often that Robert Merton, a sociologist of science, put a name to the phenomenon: multiples. One famous multiple is calculus, which was simultaneously “discovered” by both Isaac Newton and Gottfried Leibniz in the late 17th century. More recently, the accelerating expansion of the universe was observed at nearly the same time by two competing groups of astronomers, both of which were honored with the Nobel Prize in physics in 2011.
Higgs, Brout, Englert and the rest were continuing a tradition that is as old as physics itself. But why is “Higgs” the name that stuck? “Higgs expressed the challenge”—how do we get particles that have mass and still obey the rules of symmetry?—“and the expected solution especially sharply,” says Kaiser. Another recounting pins the name on Ben Lee, a physicist who used “Higgs” as shorthand in a 1972 Fermilab conference program after having had a productive lunch chat with Higgs.
Higgs himself has always been uncomfortable seeing his name ride solo. He prefers to call the particle the “scalar boson” or the “so-called Higgs,” Ian Sample writes in his book “Massive.” Higgs has also advanced the uncommonly inclusive acronym ABEGHHK’tH—that’s the Anderson, Brout, Englert, Guralnik, Hagen, Higgs, Kibble and ‘t Hooft—to honor all the scientists who played a part in originating the theory.
Frank Wilczek, a Nobel prize-winning physicist who has named a few particles of his own (anyons and axions—the latter inspired by a laundry detergent), thinks that the alphabet soup solution would be “especially absurd.” Says Wilczek: “History is complicated, and wherever you draw the line there will be somebody just below it!”
If the Higgs discovery is confirmed, though, someone will have to draw that line—and that someone will be the Nobel Prize committee. The discovery is seen as a shoo-in for the physics honor, but the prize can be divided among no more than three laureates. There are at least six scientists with reasonable claims on the Higgs—not to mention the cast-of-thousands teams whose instruments are responsible for the experimental evidence that the Higgs actually exists.
Complicating matters is physicists’ anarchic naming methodology. When astronomers have planets, moons, and asteroids in need of naming, they turn to the International Astronomical Union. Elements get their formal names from the International Union of Pure and Applied Chemistry. Physicists, who have no such official naming body, have historically opted for descriptive names, like “neutrino” (“little neutral one”), or names devoid of any physical meaning at all, like “up,” “down,” and “charm.” As a particle named after a person, the Higgs is essentially alone among the fundamental elementary particles.
So what should we be calling the Higgs? “By now it's so deeply embedded in the literature that changing to another name would be jarring, and might introduce a gratuitous complication in literature searches or eventually even a hurdle to parsing older papers,” says Wilczek. If he had to choose? “A possibly better choice might be ‘zeron,’ to connote that the particle has zero quantum numbers, and in some sense is an ingredient of what we call nothingness.”
“I’d find a fancy-sounding word in ancient Greek, to give it gravitas, and then add ‘on,’” says Kaiser. In the absence of a Greek dictionary, Kaiser nominates “lardon”—a particle that makes things heavy.
Ultimately, it may come down to branding. “In business, it would be considered destructive to take a well-known name and replace it with a long-winded, technical-sounding alternative that no one has heard of,” wrote the editors of Nature in a recent editorial. Indeed, “Higgs” seems to have captured the public imagination—and it makes a much better Twitter hashtag than #ABEGHHK’tH.
Now it’s your turn: If you could rename the Higgs, what would you call it?
Editor's picks for further reading
Facebook: Peter Higgs
No, you can't "friend" him, but you can "like" him.
FQXi: Higgs Almighty
Whatever you call it, please stop calling it the “God particle,” says blogger William Orem.
PHD Comics: Higgs Boson Explained
In this video, particle physicist Daniel Whiteson at CERN explains how the LHC is searching for the Higgs boson.