The combination of summer ATLAS and CMS Higgs results has finally appeared today (see here and here). This was originally supposed to be ready back in August, and has been circulating in various versions for quite a while. The bottom line (95% exclusion for 141-476 GeV) was mentioned here last week. They also quote limits using a much more stringent standard (99% exclusion for 146-443 GeV, excepting three small regions). Also worth mentioning is the 90% exclusion result, which reaches down to 132 GeV, leaving a SM Higgs possible only within the region 114-132 GeV.
What everyone really wants to know is when the experiments will release results based on the much larger full 2011 data set. Today’s HCP 2011 talk just says:
LHC experiments will analyze the x3 data already collected before 2012 Winter Conferences.
Tevatron will provide the final results on 10 fb^{-1} by the 2012 Summer Conferencences.
On the same time scale, there will be a combination LHC + Tevatron.
On this schedule, a possible 95% Higgs exclusion would not happen before next summer. However… I’ve seen comments from Fermilab that they should have results ready for Moriond in early March, and they expect to be able to rule out the Higgs at 95% (if it isn’t there), over the relevant mass region. More immediately, the LHC experiments have been tasked to provide updates of their Higgs results, including per/experiment combinations, for the CERN Council Week (December 12-16). Rumors from the two experiments indicate that one experiment is seeing no excesses that could be attributed to the Higgs, the other only a very small number of events in one channel (ZZ->4l). It seems not impossible that the results available (publicly or not…) mid-December will come within striking distance of ruling out the Higgs (at 90% or 95% level) over the relevant low mass range.
One interesting aspect of today’s data release is that it agrees closely with what Philip Gibbs put together back in September. For more about this, see here, especially this plot. In the past, many have speculated that the first observation of the Higgs would be reported on a blog. Now, it’s looking not unlikely that a possible exclusion of the Higgs will be first reported at viXra log…
Update: CMS has released a video including footage of their internal discussions back in August when they decided not to release the ATLAS/CMS combination. There’s no real explanation of what changed, but by November people’s concerns had been addressed and they decided to release the combination.
But Peter, isn’t news that the FTL neutrino experiment has been duplicated at CERN worthy of comment? Everybody’s talking about it….
Kid Icarus,
The experiment was not duplicated. It is the same OPERA experiment that did the measurement not another independent experiment. What they did was to repeat the measurement with very short beam pulses from CERN, which allowed the extraction time of the protons that lead to the neutrino beam. Since this more precise measurement did not change the conclusion the only thing one can say is that this specific source of systematic error was not responsible for the anomaly. Does not mean that there aren´t others. Until another experiment confirms it (most likely disprove it) the best bet is still a unknown source of systematics.
Kid Icarus,
As Bernhard points out, this is just the same experiment, with one of many sources of error removed. I still don’t believe the result, and think it’s getting way, way, way too much attention for something that is almost certainly wrong. Then, there’s the added fact that I don’t know anything much about the experiment, so it would be silly for me to write much about it here. As in many cases like this, I urge anyone interested in HEP to also follow the Resonaances blog, as well as Tommaso Dorigo’s. They actually know something, and in this case I think Tommaso knows some of the people involve and has spent some time trying to understand the result. He has a bunch of postings up about it, I’m not going to compete with that…
On the other hand, the Higgs story seems to me incredibly exciting, I can’t figure out why people would rather talk about superluminal neutrinos at this moment in history…
And back to the Higgs, if the SM Higgs is excluded we are probably going to see a huge increase of interest in WW scattering.
Bernhard,
Some of us expected some increase of interest in WW scattering already, but alas, few actually seem to care.
Just remember to catch the bear (SM Higgs exclusion) before selling its skin (strong WW scattering). And please relax: this is science, not football.
Tommaso Dorigo reads the same charts and thinks the Higgs will show up at 119 GeV.
http://www.science20.com/quantum_diaries_survivor/lhc_combination_higgs_limits_mh141_gev-84800
“In the lower part of the figure you see (black curve with blue “one-sigma” band overlaid) the “best fit” Higgs cross section, again in SM units. Here you see that while the 135-150 GeV fluctuation is only consistent with a Higgs boson that has a cross section much smaller than SM predicts, the 120 GeV one is in the right range: in other words, a 120 GeV Higgs (or rather, 119 GeV Higgs, as I predicted some time ago) would fit the bill quite nicely.
At the 2012 winter conferences ATLAS and CMS will present their search results employing three-times more statistics -all the data collected in 2011. By then we will know more about the possibility that the 120-GeV fluke is the real thing. “
Meanwhile an antagonist chooses to highlight this: the scent of SUSY wafting from CERN:
http://arxiv.org/abs/1111.4204
anonyrat,
I agree with those authors that there is a smell coming from SUSY these days, I just wouldn’t describe it as a “delicate perfume”…
Any respectable theorist, whether working on SUSY or not, knows what it means that somebody says SUSY is nearly killed. Being a polite mouse I will spare our host that knowledge.
I don’t know if this is something anyone should worry about or not, but I figured I could ask here. I also know that consensus isn’t a gold standard of anything in science, but there appear to be very few serious physicists who wouldn’t agree that something simply must be going on at the TeV to break electroweak symmetry. The odds in favor of nothing showing up in the LHC appear to be pegged at about the same quantity.
So, fine, if the Higgs is about 120 GeV, that’s a fiendishly difficult range for a hadron collider to probe, and it will take a lot more data. Still, some folks are apparently starting to get a little worried. Let’s say that fluctuation vanishes. Let’s say we see nothing else either.
Out of necessity, only a tiny fraction of collision data is captured, and those events are screened according to some entirely justifiable, but undoubtedly biased, criteria. When do we have to start wondering about missing something? Could a real signal be thrown away?
LMMI,
I’m sure the current triggering choices being made at the LHC are designed to be optimal for looking for a SM Higgs signal. If it turns out there is no SM Higgs signal, then the question of what the LHC should be looking for to understand electroweak symmetry breaking will become a very important one. One answer will be “some SUSY or multiple Higgs model in which the Higgs is harder to see”, and if triggers start being designed to look for these, one might worry about that.
In general though, I think the LHC experimentalists can be relied upon to not pay too much attention to theorists, and design triggers most optimal for picking out interesting classes of events. But in principle the possibility does exist that electroweak symmetry breaking comes from some source we haven’t thought of, one that the LHC triggers aren’t sensitive to
… “some SUSY or multiple Higgs model in which the Higgs is harder to see”… Are there leading candidate theories (references?) for such SUSY or multiple Higgs models?
For a good overview of many possible such models, see Matt Strassler’s page
http://profmattstrassler.com/articles-and-posts/the-higgs-particle/implications-of-higgs-searches-as-of-92011
The problem is that none of these models are well-motivated (i.e. no evidence at all indicating them, and they’re significantly more complicated than the SM: you’re adding lots of new particles for no good reason other than to avoid conflict with experiment).
I feel obliged to correct our kind host on this very common misunderstanding he repeats time after time: SUSY versions of the SM are not more complicated because you have to add lots of new particles which are not well motivated. The spectrum is doubled due to a fundamental hypothetical new symmetry of the world, which is something altogether different. I guess our kind host in his daily life multiplies 2×13 by summing one by one from 13 to 26.
Anonymouse, are you saying when you double a quantity, you are not adding anything to it?
The Supersymmetric Black Knight “Come back here! I’ll bite your legs off!”
@Anonymouse
Its not a case of adding a fundamental new symmetry, rather a broken fundamental new symmetry. One needs to explain how the breaking occurs and this adds complications.
Anonymouse,
I was specifically answering a question about the Higgs, so, in the context of supersymmetry, the point is that no one has seen evidence of any of the multiple Higgs particles needed in that theory. So, one has to go to some trouble to hide the things, a problem that will get worse if a SM-like Higgs is ruled out.
More generally, as Dave points out, what makes supersymmetric extensions of the SM complicated is not the doubling of degrees of freedom, but the huge number (>100) or parameters that must be introduced to describe supersymmetry breaking. In the world of SUSY-dreams, some new physics will be found to dynamically break SUSY and determine those parameters, but even in SUSY-dreamland, the new physics that does this will make for a significantly more complicated theory than the SM.
@ Anonymouse
Most of the SUSY spectrum not already excluded requires a light Higgs just as much as the SM does. A Higgs exclusion greatly squeezes the parameter space of these models as well, arguably more, since its mass spectrum is more tightly constrained theoretically.
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I would like to note that four years ago I proposed a modification of SM in which the Higgs becomes unobservable. In this modification, in which a Weyl gauge field is introduced, manifest covariance, renormalizability, and unitarity are maintained. See, N.N., Prog. Theor. Phys. 118 (2007), 913.
N. Nakanishi,
Are you saying your idea is to have the SM with a mechanism to avoid a possible conflict with experimental data? With no disrespect but that sounds not too impressive. Unless this extension actually produces a measurable difference that can be cached, either than one that cannot, this does not seem to improve our understanding of what´s going on.
Bernhard,
Have you read my paper (arXiv: 0704.2645v2 [hep-th])?
If the Higgs is not found experimentally at all, do you have any idea rescuing SM?
ZZZ:
What the mouse says is that claiming SUSY adds too many new particles misrepresents the idea.
Chris Oakley:
Nice clip. Love those guys. But life may improve over art: keep posted.
Dave:
You’re right, that’s the ugly side of it, not the doubling of the spectrum. But this will turn out to be an opportunity to learn, once we have experimental access to the details of the spectrum.
Peter:
You’re now completing your previous misleading reply, but you cannot help
your dislike of SUSY showing through. People don’t try to “hide things”. They try to figure out how the theory might be guided by experiment. There is a world of difference between these opposite ways of putting things. You are transmitting the message that scientists are cheating and fooling themselves while I know many honests physicists who are just trying hard to figure out things. You do a disfavour to science.
Concerning the huge number of parameters related to SUSY breaking that’s just the low-energy point of view, which would be wrong to use if you want to gauge the complexity of your theory. You can’t say much about how complicated SUSY breaking is till you have experimental information about the spectrum. People also forget that SUSY could’ve been dead long ago, e.g. if it predicted that scalars should be lighter than fermions. Or disfavored if it predicted the wrong running of gauge couplings.
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N. Nakanishi ,
Now I did, nice paper. I was indeed expecting that any model that would make the Higgs unobservable clearly predicted something else and your model cleraly does that:
“in addition to the physical absence of the Higgs boson, slight violationof Lorentz invariance and the existence of a new massive gauge boson.”
So that is fine, your first comment made me jump to the wrong conclusion but I anyway should have looked with more attention before criticizing it.
The requirement of unitary and renormalizability always implies something extra to be discovered beyond the SM. If LHC doesn’t find anything new, this means that these requirements are too strong. In fact quantum gravity ( and Nature ) is in conflict with these requirements and works fine without them.
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