A joint Fermilab/SLAC publication

Not the Nobel, but Higgs shares major theoretical physics prize

10/05/09

With the announcement of the 2009 Nobel Prize in Physics due tomorrow, there has been much speculation about who the winner(s) might be. Companies like Thomson Reuters, who sell their scientific citation database information, always get a bunch of publicity for their predictions based on citations, although there is some evidence that the power of citation counts for predicting the physics prize is weakening.

Regardless, there are many people who think that a Nobel Prize will be awarded for the Higgs particle. But what prize precisely and to whom? There is the theoretical development that was published by three groups in 1964, and the possible experimental finding that could come in the next few years.

At the moment, there is no particular incentive for the Nobel committee to rush through a Prize honoring the theoretical development unless they want to look like they are ahead of the game with experimental discovery potentially imminent. Back in 1997, groups led by Eric Cornell, Carl Weiman, and Wolfgang Ketterle all created long-sought Bose-Einstein condensates in gases of alkali metal elements. And many speculated they would win the Prize. Instead, their discovery was quickly followed by the award of the 1997 Nobel Prize in Physics to Steven Chu, Claude Cohen-Tannoudji, and Bill Phillips for the experimental technique of cooling and trapping gases using lasers. Cornell, Weiman, and Ketterle won the prize themselves in 2001. So perhaps there could be a prize for Higgs theory first, but they committee might wait until the experimental discovery to make sure they are right. After all, the Higgs mechanism might not be the right approach to explaining how particles get mass, although it has been incredibly powerful in the development of particle physics ideas. The Nobel for the theoretical development of the electroweak theory was awarded prior to the discovery of the W and Z bosons that gave the solid evidence it was correct so there are precedents either way.

But let’s suppose that the Nobel committee wants to award a prize for the theoretical work behind the Higgs mechanism. They would probably want to recognize precisely the group that has just won the 2010 J.J. Sakurai Prize, awarded by the American Physical Society. That prize will be presented in February at the APS “April” meeting in Washington, DC, but has been announced as going to Carl Hagen, Francois Englert, Gerald Guralnik, Peter Higgs, Robert Brout, and Tom Kibble "for elucidation of the properties of spontaneous symmetry breaking in four-dimensional relativistic gauge theory and of the mechanism for the consistent generation of vector boson masses."

These guys all published papers in Physical Review Letters in 1964 that essentially described how quantum field theories could predict particles that had mass. (Here are the papers by 1) Guralnik, Hagen, and Kibble, 2) Higgs, and 3) Englert and Brout.) That was a big deal because there was a famous theorem by Goldstone that showed quantum fields which had continuous symmetries must have a massless particle associated with them. At the time, physicists thought that the main example of this is how the electromagnetic field has a photon associated with it (although they later learned that the problem was more subtle).

Physicists, however, were troubled by an obvious conflict with reality. The weak force seemed to require particles that have mass (or else it wouldn’t be so weak and have such a short range). How could that mass come about? In essence, the researchers identified a loophole in the Goldstone theorem, which remains true as long as all the assumptions hold. Those assumptions are quite subtle, however, and it turned out that you could create a quantum field theory, that had what are called spontaneously broken symmetries, which still obeyed all the laws you needed to obey. These new theories had particles which obtained their mass due to an interaction with another field. It is called the Higgs field in the case of describing how the W and Z bosons are thought to get their mass.

Each of the groups took a slightly different approach and all added to the general development of the theory which has been so powerful in theoretical particle physics ever since. However, the name of Higgs has stuck with the approach, and we should probably be grateful that we don’t need to call it the Hagen-Englert-Guralnik-Higgs-Brout-Kibble particle, and watch physicists quibble for years over what order they chose for those names. (I’m using them in the order that the APS uses to list them in the announcement of the Sakurai Prize, before you attack me for playing favorites!)

In the end, what does this mean for the Nobel committee? It seems difficult to select out a subset of these six and just recognize three of them. The problem of too many possible recipients has resolved itself in the past with time as the physicists age and eventually a set with three or fewer members alive remains to receive the prize, but that doesn’t seem like a particularly sensible strategy. There is a sense in the air that some action is coming soon and many in the particle physics community see the preprint by Guralnik earlier this year as an attempt to try to reinforce the GHK contribution to the theory. Others in the physics community are likely to champion certain combinations of physicists, and back in the early days of symmetry we saw an expanded list (adding Anderson and Nambu to the list of six) mentioned by Joe Lykken in a story about how physicists name particles, facilities, and phenomena.

So what will happen tomorrow? My guess is that the Nobel committee will avoid dealing with the difficulty of too many recipients for the time being and at least wait until there is movement on the experimental front of the Higgs search. Recognizing only three recipients for an experimental discovery will present a monster, and undoubtedly controversial, challenge for the Nobel committee. Given the recent history of prizes, I’d probably guess we’ll see something in the quantum optics/quantum fundamentals arena announced for tomorrow.

Until the contributions to the Higgs mechanism are all sorted out though, it is great to see the group of six recognized with this major prize from the APS, even though it will be overshadowed by the Nobel announcement.

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