Higgs, Higgs, Higgs

I’m trying to get over my Higgs obsession, and move on to other topics, but one last posting about this for now…

The first thing to say is that this is the biggest thing to happen in fundamental physics in about 30 years (i.e. since the discovery of the W and Z). It’s a remarkable event and huge success for high energy physics, vindicating at the same time the colossal efforts that have gone into making the LHC and its detectors work, as well as the theoretical framework of the electroweak part of the Standard Model. Today’s New York Times has a front-page story by Dennis Overbye, above the fold, which is very well done. In general the press reports that I’ve seen have been quite good, with minimal speculative nonsense thrown in. According to Overbye, CERN DG Heuer made the right decision to go ahead and simply claim discovery only on Tuesday afternoon. All in all, CERN has done an excellent job of communicating this story to the public (except perhaps for the “don’t believe the bloggers” business, but what else could they do…).

Attention will turn now to who gets rewarded for all this, in particular, who gets a Nobel Prize? Personally I think the experimentalists are first in line, and with no obvious figureheads, a prize for three groups: ATLAS, CMS and the CERN accelerator engineers and physicists would be highly appropriate. If it’s not too late in their process, maybe this could even be done in time for this year’s prize, announced October 9.

As far as theorists go, Frank Close has posted something about this here. With the restriction to three people, he argues for Englert, Higgs, Kibble. Personally I think Anderson deserves a piece of it, see here. There’s also a good argument to be made that what has just been validated is not the older work on the Higgs mechanism, but the Weinberg-Salam model of 1967 (extended to quarks), and that has already been rewarded with a Nobel.

I’ve been trying to get accurate numbers for the signal sizes seen by CMS and ATLAS in the various channels, but the only information out there now is the slides from the two talks. Resonaances includes the crucial plot from each experiment giving the signal sizes normalized to the SM, and eyeballing these and averaging, one gets 1.0 in the ZZ channel, 1.75 in gamma-gamma channel, about .75 in the WW channel (only CMS reports 2012 data). In the bb and tau-tau channels, no significant signal is seen, but the expected signal size there is very small. The errors per experiment are something like +/- .4, which you can make your own judgement about how to reduce for the combination. The bottom line is that, within errors, everything is consistent with the SM predictions. The gamma-gamma channel is the one to watch, it is about 2 sigma high.

The DG also announced a new LHC schedule, extending this year’s proton-proton run by two months, to mid-December. This will hopefully allow the experiments to each accumulate another 20 inverse fb of data, finishing this run and going into a two year shutdown with a total of 30 inverse fb to analyze and use to improve the results on the Higgs.

While this announcement is a great triumph for physics, unfortunately it significantly increases the probability of what has become known as the “Nightmare Scenario”: a SM Higgs discovery and nothing else at LHC energies. Before the LHC results started to come in, this scenario and its consequences was easy to ignore, but we may be getting closer to the point where it needs to be taken very seriously.

Update: For a rather complete analysis of the data about the different Higgs decay channels, see this new preprint.