Over the past two days, CERN has been hosting a program consisting mostly of talks by Nobel prize winners in high energy physics, under the title 50 Years of Nobel Memories in High Energy Physics. It has been a while since anything Nobel Prize worthy has been discovered in HEP, so the speakers of necessity are all getting on a bit in years. The talks pretty much all seem worth paying attention to. Many of them are now on-line, and of the few I’ve had a chance to look at, the comments by Burt Richter about the ILC/CLIC issue were notable, as well as Veltman’s explanation of the possible significance of not finding a Higgs.
I started watching the webcast towards the end of David Gross’s talk, in time to hear him give his usual praiseworthy defense of physics against anthropic pseudo-science. Weinberg’s talk by video-conference was unfortunately cut short, since he thought it would be an hour long, but it was just scheduled for half an hour.
CERN DG Heuer ended the program by thanking everyone, and looking forward to the first run of LHC collisions at reasonable intensity with the detector magnets on (although only at 450 GeV), which is now scheduled for Saturday.
Update: Videos of the talks are now available here and I’ve watched a few of them. One interesting thing I noticed was Frank Wilczek’s talk about QCD, where his response to a question about AdS/CFT was “I’m not as impressed as I should be.”
Gall et al’s (or is it al et Gall?) observation about the Nobel prize singulariaty is quite on the spot.
Newbie question after reading Glashow’s talk: he says that “Furthermore, the Higgs mechanism per se cannot fully explain electroweak symmetry breaking.” What is meant by this?
Re ‘it has been a while since anything Nobel Prize worthy has been discovered in HEP, so the speakers of necessity are all getting on a bit in years’
it seems the time gap between theory and experiment gets larger the deeper down we go. Sad to think whole careers come and go in this timeframe e.g. if supersymmetry is observed at the LHC, almost none of the pioneers will be around to see it (except Zumino)
Domenic,
I’m not sure what Glashow had in mind. There are various problems of principle with introducing an elementary scalar Higgs field (it’s not asymptotically free, cosmological constant), there’s the hierarchy problem, then there’s the basic problem that you lose all ability to predict particle masses, since they are given in terms of arbitrary Yukawa couplings to the Higgs.
http://insti.physics.sunysb.edu/~siegel/parodies/sam/sam.html <– Check out the section called Nobel Prize Singularity.
The schedule for the weekend (http://lhc-commissioning.web.cern.ch/lhc-commissioning/news/LHC-news.htm) is interesting – 450GeV collisions mixed with ramps (presume to 1.18TeV).
Hopefully if all goes well, they might just tweak the schedule a bit to collide at the higher energy as well…
Peter, I don’t see a link to the videos of talks. Could you(or others) point me to it?
Thanks
shantanu
Shantanu,
I watched some of the talks on the live CERN webcast site. Presumably the videos will be made available later, but I don’t think they’re up now.
I don’t understand why time would be an issue and they have to cut Weinberg’s talk in the middle. It is a singular opportunity to preserve for posterity the talks by these great scientist. I think CERN should do more in this regard.
So are there any seriously considered alternatives to higgs (simple scalar or composite?)
dan,
The general assumption is that, to get electroweak symmetry breaking, one needs to add some sort of new fields to the fermions and gauge bosons of the standard model, with dynamics such that either an elementary or composite field gets a vacuum expectation value that breaks the symmetry. The most popular ways to do this are an elementary Higgs scalar, or a new QCD-like sector, with pions playing the role of the Higgs field (technicolor). I don’t know much about other ideas, the prejudice seems to be that they end up being equivalent to one of these two alternatives.
It wouldn’t surprise me though if it turns out that electroweak gauge symmetry breaking is a much more subtle business, with some currently unsuspected way of making it work. Hints from the LHC about this would be most welcome…
Thanks for replying,
I know that SUSY is the proposed solution to simple scalar higgs fields, the other is fine-tuning, but do technicolor models (i.e top color assisted technicolor) or composite higgs field also suffer from the hierarchy problem, and need SUSY or fine-tuning to remedy them?
Is there a reason SUSY seems preferred to fine-tuning?
dan,
Other than the problems with elementary scalar fields, it’s not clear to me that there really is a hierarchy problem. One has no evidence for a GUT scale, nor an understanding of quantum gravity, so the smallness of the electroweak scale relative to these may not be of any particular significance.
Thanks, just to clarify, if there is no GUT or planck scale, then Higgs large radiative contributions do not apply?
Hi Dan,
The large radiative corrections do apply, even if there is no GUT or planck scale. I presume that what Peter has in mind is that there is some ‘subtle’ property of QFT that is currently not recognized which would make these corrections small. I presume he applies the same logic in his idea that electroweak symmetry breaking will not involve a Higgs-like mechanism.
dan,
The “large radiative corrections” problem is a problem with having an elementary scalar field. It’s just one of the reasons for not being happy with this way of implementing electroweak symmetry breaking.
Are there serious proposals for breaking electroweak symmetry breaking that do NOT involve elementary scalar fields and is also consistent with current evidence such as W-W scattering?
thx in advance
dan,
I don’t think current data about WW scattering constrains much of anything, my understanding is that this is something interesting to look at at LHC energies. Technicolor and its variants are the most well-known alternatives to scalar fields, long ago I had a guest blog entry here from Robert Shrock about the state of constraints on such models, see here:
http://www.math.columbia.edu/~woit/wordpress/?p=614
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