The Hadron Collider Physics Symposium will be next week in Kyoto, with announcements of new results from the LHC, some details of which are starting to trickle in. Chris Quigg explains what to look for here.
The LHC has just recently passed the milestone of 20 fb-1 of data at 8 TeV this year. Perhaps this will get up to 25 fb-1 by the end of this run later this year. After a heavy ion run early next year the machine will go into a long shutdown (until late 2014) for repairs to allow operation at close to design energy (probably at 13 TeV). Next week results will be reported based on 12 fb-1 (CMS) and 13 fb-1 (ATLAS) of this year’s 8 TeV data (compare to this past summer’s results based on 5.3 fb-1 (CMS) and 5.9 fb-1 (ATLAS)). Expect results from the full 2012 data at Moriond in March, with an official combination of results from the two experiments next summer.
On Monday LHCb will report the latest results on B(s)->mu+mu-, and the latest Higgs news should come at the Higgs parallel session on Wednesday. There will also be quite a few new, stronger limits on SUSY.
I’m hearing that these new results already can rule out the idea that this new particle is a pseudo-scalar. There will be no confirmation of an unexpectedly high gamma-gamma rate. Some excesses in the tau-tau channel are being seen, of roughly the size you would expect for a SM Higgs. So, all in all, things are still consistent with a SM Higgs. If not, please let me know….
Update: The B(s)->mu+mu- results from LHCb are out (see here), providing good agreement with the SM, and new, strong limits on possible SUSY models (see the last slide). More from Matt Strassler and Michael Schmitt.
For another source for new LHC results, together with interpretation of their signficance, the Chicago 2012 Workshop on LHC Physics is starting today.
I wonder if Atlas will report the 3 GeV difference they observe in the Higgs peak for different channels…
Dr. Woit, your writings over the last year make it seem as though CERN is pretty close to being able to refute SUSY. I’m curious to know what you think will be the timeline for the death of SUSY, and maybe what you think the community reaction will be. You’ve posted some interesting examples of denial, but when do you think a prominent SUSY theorist will come out and say that this is probably not the way our world works?
I’m somewhere between a layperson and a physicist (I’m a PhD candidate), and I have seen no evidence to believe in SUSY. I don’t believe in it because the little I have comprehended seems ‘not crazy enough’ (as Wheeler once said). When can I claim that my view is scientifically valid?
Since the “death of SUSY” is a topic covered to death on this blog, I’d rather not go on about it more at this time, but stick to the topic of the upcoming conference. The progress of the SUSY community through the various stages of grief, from denial to acceptance, has already started, but I’ve no predictions about how it will play out over the upcoming months and years (other than the obvious one that some people will never give up, no matter what the evidence against them is…)
can you please be more specific on “There will be no confirmation of an unexpectedly high gamma-gamma rate. “
Not unless someone sends me some more specific information. One rumor though is that there’s still some argument on the numbers that will be reported about this…
Like other wrong ideas, SUSY will die one supersymmetrist at a time.
Rumor has it ATLAS is going to be cautious about saying things because their measured Higgs masses in the ZZ and gamma+gamma channels differ by enough that they’re concerned about miscalibration somewhere. Rumor also has it that at CMS, the gamma+gamma excess is smaller now. As most reasonable people would have expected….
(I hadn’t heard the tau news. That’ll be a nice addition to what we know.)
There is in principle no way that LHC or any other machine that operates at a certain finite energy can refute supersymmetry, since one can always claim that susy is broken at a sufficiently higher energy level to be observed.
What one can do is to argue that susy is broken at such a high energy that its presence makes no difference to observable phenomena. When that is the case, the only justification of susy becomes the mathematical consistency of certain models, such as strings.
“Like other wrong ideas, SUSY will die one supersymmetrist at a time.”
Sorry, I don’t think it’s possible for SUSY to die at this point. It makes no difference if it doesn’t show up at the LHC because supersymmetric quantum field theories are important for theoretical reasons. For one thing, they’re the easiest theories to analyze mathematically because you have techniques like localization at your disposal. Supersymmetric theories have applications in physics (like Witten’s proof of the positive energy theorem in classical general relativity), and they also have many applications in pure mathematics (proofs of the Atiyah-Singer index theorem, the Morse inequalities, applications to elliptic cohomology, Donaldson theory, and the geometric Langlands correspondence). If you really think SUSY is going to die, you’re getting too much of your information from this blog…
If it can’t die, it’s not science. (Sorry for the repetition. On the one hand it’s not going to make a difference, on the other hand it has to be said.)
An interesting question would be: Should we keep an idea alive in physics because it seems to be fruitful in certain branches of mathematics?
Bob Jones, thank you for the illustration.
“If it can’t die, it’s not science.”
I completely agree.
“An interesting question would be: Should we keep an idea alive in physics because it seems to be fruitful in certain branches of mathematics?”
That is an interesting question, but it’s also somewhat hypothetical because ideas like supersymmetry and string theory are not only useful in mathematics. They also have tons of applications in physics. In addition to the examples I gave above, you also have applications of N=4 gauge theory to QCD. That’s a hugely important topic in physics where supersymmetry comes up.
The latest LHC schedule:
So two more weeks of running, adding another 2/fb, and then final three weeks for major machine development and 25ns development. It looks as if they should deliver between 22.5-24/fb for 2012
Please, enough about SUSY unless it’s about the HCP2012 conference.
My reference to “death of SUSY” was short-hand for “death of SUSY extensions of the SM that have dominated the field of BSM physics”. The fact that there’s a much more complicated and interesting story about SUSY in general is one reason I don’t think it’s a good idea to discuss it here, where it’s far off-topic, and the actual topic is I think both interesting and highly timely.
Bob Jones wrote: “Supersymmetric theories have applications in physics (like Witten’s proof of the positive energy theorem in classical general relativity)”.
It is quite a stretch to call Witten’s positive energy proof an application of supersymmetry. True, Witten’s original article discusses a motivation coming from supergravity (quote: “a few speculative remarks will be made about the not altogether clear relation between the previous argument and supergravity”). But that is certainly not the most natural way to think about it. The natural way to think about it is this: In the early 1960s, Lichnerowicz — not thinking about SUSY in any way whatsoever — had showed by spinorial methods that certain closed manifolds do not admit Riemannian metrics of positive scalar curvature. Witten’s proof is closely analogous to Lichnerowicz’ argument, dealing with asymptotically flat manifolds instead of closed ones.
If you really want to interpret Witten’s proof in a field-theoretic way, you should notice that the only field involved is purely fermionic: a spinor on a 3-dimensional spacelike surface.
I would argue that certain other presumed applications of supersymmetry in mathematics, for instance Seiberg-Witten theory, do not have to do anything with SUSY either. Yes, Columbus found America while he wanted to get to India; but America is very far from India, and travelling westwards from Europe, you arrive at it naturally, no matter whether you are heading for India, China, or the setting sun.
Saying that Witten’s positive energy proof or the Seiberg-Witten equations are applications of supersymmetry is like claiming that Teflon was a spin-off of the NASA space missions, or that Newton’s gravity theory would not have been discovered without apple trees.
I presume that doubling the data will fine up the range of potential masses and other characteristics of the particle. The existence of the Higgs itself, and a general mass range are of obvious importance and appears to have been achieved.
Which leaves the question, (which I hope is not too far off topic): how much practical, computational (?), difference will the reduction of the + or – of the mass by a couple of percentage points mean vis a vis any current theoretical perspective?
The interest now isn’t so much in getting a more accurate Higgs mass, but in seeing the Higgs in different channels and measuring the production cross-section x branching ratio in each of those channels. Any deviation of those from the SM predictions will indicate new physics: either new particles, or a different coupling between the Higgs field and other SM fields than expected.
Regarding B(s)->mu+mu- I found the following useful for context http://muon.wordpress.com/2012/11/10/watching-for-bs-to-mumu/
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Thank you for the explanation, and for the link.
Interesting–and beautiful graphic.
Slides have appeared for today’s talks here http://kds.kek.jp/conferenceDisplay.py?confId=9237 and those on new results for B(s)->mu+mu- by Johannes Albrecht seem to say: (1) first evidence for decay (3.5σ level) (2) data disfavours constrained SUSY at high tanβ.
The BBC have picked up on this, reporting that “[The existence of SUSY] would help explain why galaxies appear to rotate faster than the Standard Model would suggest”.
Dr. Woit I’m curious to know: what in your view will probably replace SUSY in being a solution to a variety of problems?
Ha. Funny. Even The Register has gotten in on this one:
I don’t think SUSY ever actually provided a solution to important problems in HEP. This is a long story, which I wrote about extensively in my book (written ten years ago). I pointed out that the case for SUSY was weak back then, it certainly hasn’t gotten any stronger.