I was busy with some personal issues over the past few weeks, so I hadn’t even really been following the rampant speculation about the Nobel Prize for this year. Apparently a lot of people (including some of my colleagues) thought that the July discovery, at the Large Hadron Collider [LHC] experiments ATLAS and CMS, of a new particle resembling the long-sought Higgs particle would generate a Nobel Prize in 2012 for Peter Higgs and for the other physicists who predicted the existence of such a particle.
Well, I never thought this notion was very plausible; I was confident it wouldn’t happen before 2013. And that is for several reasons.
The first and most important is that although the evidence that a new particle has been found is very strong, the evidence that it is a Higgs particle of some type (which I’ll describe below) is still only moderate. Personally, I’m convinced that the new particle is a Higgs particle, but that is based partly on the evidence from the data and partly on theoretical prejudice — on my knowledge of theoretical physics and of what the alternatives to the Higgs-particle interpretation of the data are. If I’m wrong, too bad for me, but no harm done. However, the Nobel Prize committee is making a permanent, irrevocable award for the history books, and the bar for evidence from the data alone should be very high. Now here’s the key point: by March 2013 at the latest, the data from all of 2012 will have been analyzed. The amount of data that will be available by then will be about three times as much as was available in July 2012 — enough to change the current moderate evidence to strong evidence, if in fact we’re dealing with a Higgs particle of some type. The Nobel Prize committee is surely well aware of this — that by next year the situation is likely to have qualitatively changed, with the evidence beyond controversy. So it makes sense to wait until 2013, when the case is likely to be closed.
Before I go on, let me explain why I say the evidence that the new particle is a Higgs particle is only moderate. [Again, it is enough evidence to convince me, but that's because of my theoretical prejudice.] Recall that the simplest possible type of Higgs particle is called the “Standard Model Higgs”, but the Higgs particle in nature may be more complicated, and there might even be several Higgs particles. Now, there are three lines of evidence:
- Very weak evidence from other measurements: Precision measurements of many types can be combined together to make an indirect prediction that the Higgs particle, if it is of Standard Model type or similar, should have a mass below about 200 GeV/c2. This evidence requires assuming something about the Higgs, rather than taking the information from LHC data directly, and its prediction isn’t precise.
- Weak evidence from photons: the observed rate for this new particle to be produced and then to decay to two photons is within a factor of two of the rate expected for a Standard Model Higgs particle. The problem is that other particles could (by accident) have a similar rate.
- Moderate evidence from leptons: the observed rate for this new particle to be produced and then to decay to two lepton/anti-lepton pairs is within a factor of two of the rate expected for a Standard Model Higgs particle. The reason this evidence is stronger than the evidence for photons is that it is very difficult, for deep theoretical reasons, to arrange for any non-Higgs particle of 125 GeV/c2 in mass to have such a large probability to decay to lepton/anti-lepton pairs. However, this evidence still rests on only a handful of observed collisions — few enough that it is still conceivable, though very unlikely, that they could be due to a statistical fluke.
Looking ahead, the best evidence that this is a Higgs particle will continue to come from its decays to lepton/anti-lepton pairs (with additional evidence from other sources playing a supporting role.) With three times the data, the probability that the observed events are due to a statistical fluke will drop very significantly, and other tests of the Higgs-particle interpretation of the data will become possible. And so the moderate evidence from leptons that we saw in July will likely be very strong by the time it is updated in March. If I were on the Nobel committee, I’d want to wait until after March, just to be sure.
There are two other reasons why the committee might have wanted to wait. The first is that it takes some considerable time to put together a case for a prize; it is a big logistical job. From early July to early October (with August a vacation month) would not have left much time, even for a normal prize award. The second is that the committee has an especially thorny problem with the Higgs particle. There are clearly six people involved: Higgs himself wrote papers, but these were essentially simultaneous with papers by Englert and Brout and by Guralnik, Hagen and Kibble. [Anderson, whose papers in solid state physics about superconductivity partly presaged the Higgs field idea, already has a prize for something else.] Brout, unfortunately, has died, too soon to know of his achievement. But the Nobel Committee has never given a prize to more than three people (as a consequence of which some important people, such as B.J. Bjorken, have never received a Nobel Prize for their work.) So they either have to change their rules, or they have to play favorites, or (bluntly) they have to let nature play favorites and wait til two of the people on the list die. Either way this is extremely controversial and it is going to take them quite a while to figure out what to do. Three months is nowhere near enough, I am sure.
Two final remarks.
The first is that the next looming giant problem for the Nobel Committee involves how to give an award for the experimental discovery of the new particle. This discovery involved perhaps the largest collective scientific effort ever undertaken; not only can it not be boiled down to three people, it can’t be boiled down to three hundred. The skills and ideas and techniques and the sweat and blood of many, many physicists and engineers went into the design, building, and operation of ATLAS and CMS and of the LHC itself, and dozens were directly involved in the measurements that allowed the discovery of the new particle. There is no obvious way to select the leaders and give them a personal prize. I don’t know how the committee is going to deal with this without changing their rules. Science has changed, in a big way; can the Nobel Prize adapt?
Second, one should remember that the six members of the Higgs crew have already won the only prize that actually counts. Imagine learning that you, a measly human being, thinking away in an office somewhere, have guessed something profound and fundamental about this great and awe-inspiring universe — something the history and science books will recount for as long as our civilization holds itself together. This is a prize that no human can award. And the physicists of the Higgs crew received this prize [preliminarily -- final confirmation by March 2013] from Nature, when the discovery was announced back in July. The money and the fame of next October’s Nobel Prize, great as they may be, are pale compared to the humbling glory and wonder of having been the incredibly lucky ones who, smart and thoughtful but nearly blind, stumbled into the truth.