Today’s Higgs Results

The discussion after the talks is going on at CERN now, and the results that were presented agree well with what was posted here over the past week or so. This looks a lot like a Higgs near 125 GeV. Hiccups in the streaming make it difficult to impossible to follow the discussion. Caught Heuer at the end urging caution: “intriguing hints”. This looks to me like a lot more than “intriguing hints”: it’s about what you would expect if a Higgs was there at 125 GeV, highly unlikely to see if there is no Higgs there.

The ATLAS results are here

Higgs to gamma gamma: 2.8 sigma bump at 126 GeV

Higgs to ZZ to 4l: 2.1 sigma (3 events near 125 GeV)

Higgs to WW to l nu l nu: Data not fully analyzed, 1.4 sigma excess at 126 GeV

Combination: 3.6 sigma excess at 126 GeV.

The CMS results are here


Higgs to gamma gamma
: 2.34 sigma bump at 123.5 GeV.

Higgs to ZZ to 4l: 2 events seen near 126 GeV (expect .5 background)

Combination: 2.4 sigma excess at 124 GeV.

I see Tommaso Dorigo is posting a detailed analysis here under the title “Firm Evidence of a Higgs Boson at Last!”. He’s likely to be the best source around for a discussion of the details.

Update: Go to the blog of Philip Gibbs now to take a look at his (highly unofficial) plots of the combined ATLAS+CMS+Tevatron results on the Higgs. You might also want to check out Matt Strassler’s blog entry about this, which wins the award for being downbeat (“Inconclusive, As Expected”). For some reason he is incensed by Tommaso Dorigo’s “Firm Evidence”.

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71 Responses to Today’s Higgs Results

  1. anon says:

    Though still too early to say, congratulations to Prof. Peter Higgs!

  2. Albert Z says:

    I would not be surprised in the least if the wheels fell off this latest Greatest Bump Hope within weeks.

    Then again, I am much less skeptical of a Higgs boson than the ad hoc “WIMPs”, since the standard model, while quite heuristic, at least has considerable empirical support.

    Albert Z

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  4. Foster Boondoggle says:

    What’s the SM width of a 125 GeV higgs?

  5. I find your response interesting, Peter. Matt Strassler seems considerably more cautious, based in part on look-elsewhere concerns and whether the CMS number (123-ish) is compatible w/ the Atlas number (126-ish). As someone with no dog in this hunt, it’ll be fun to see how this plays out, and particularly the media reaction in the short term.

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  7. Peter Woit says:

    Foster Boondoggle,

    See this comment

    http://www.math.columbia.edu/~woit/wordpress/?p=4212&cpage=1#comment-101006

    The SM width is very narrow, so the observed width is due to the resolution of the detectors. Commenter thinks 3-4 GeV. The compatibility of the two gamma-gamma signals is a very interesting issue I’d love to see a detailed analysis of, much more relevant than the “look-elsewhere” effect you need to worry about if you only had data from one experiment. My impression is that, at this level of statistics, taken together they’re reasonably compatible with a 125 GeV SM Higgs (and seriously incompatible with nothing being there at all…)

    Doug,

    Just as you can accurately describe the same glass as “half-full” or “half-empty”, you can accurately describe this as “inconclusive” or “firm evidence”. No one is claiming that this yet reaches the conventional 5 sigma level for claiming a discovery. An accurate description of the situation would be that the data shown is, given the statistics, consistent with a 125 GeV SM Higgs. It is fairly seriously inconsistent with the no Higgs hypothesis. More expertise in statistics than I have would be required to properly quantify the relative probability of these two hypotheses, perhaps that’s something that will get done publicly soon.

  8. Trulo says:

    the standard model, while quite heuristic, at least has considerable empirical support.

    Albert, in this context “considerable empirical support” is the mother of all understatements.

  9. Roger says:

    I assume that you are preparing to write a rebuttal when Kane publishes an article about how this result confirms string theory.

  10. Peter Woit says:

    Roger,

    Already done (on both sides), see the previous posting:

    http://www.math.columbia.edu/~woit/wordpress/?p=4262

  11. VP says:

    Anyone have any comments on the fact that the ATLAS bump is 126-ish and the
    CMS exclusion lower limit at 127 GeV?

  12. Peter Woit says:

    VP,

    Other than that they’re consistent?

    What I’d really be interested in seeing is some attempt to sensibly combine the two gamma-gamma datasets. Would the result have a bump statistically consistent in width and size with the SM Higgs? As far as I know the answer is yes, but I’d love to know for sure.

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  14. anon says:

    What’s the implication for possible funding of ILC?

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  16. Richard says:

    The significance of this announcement is that it is insignificant.
    The press conference was almost certainly called to defend against funding cuts that are likely in a time of austerity and Euro-stress. The HEP community has gotten quite sophisticated at PR. Big physics needs big money. With the French under pressure to cut spending, the LHC folks need some smoke and mirrors to keep the Euros flowing.

    Call me when you get to five sigma.

  17. Low Math, Meekly Interacting says:

    Assuming this is the prelude to a firm discovery, and the mass is just about what the result indicates, anyone care to comment on the potential for probing new physics at the LHC? I’ve seen some rather pessimistic assessments, i.e. this might be the harbinger of a desert all the way up to the GUT scale. A reasonable conclusion?

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  20. Peter Woit says:

    anon, Low Math, Meekly Interacting

    Knowing the Higgs mass means one can calculate exactly how well it could be studied by an ILC with different design parameters. If the LHC finds the Higgs is really there and behaves just like the SM says, and finds no other new physics, the case for not only the ILC, but any other expensive energy-frontier collider is going to be hard to make.

    In that scenario, there’s a real danger that what we saw today was the crowning achievement of this kind of experimentation, with prospects for the future rather dismal. For that reason, I and many others would have been a lot more excited if what we heard was that a SM Higgs was excluded or nearly excluded over the low mass region.

    The LHC really needs to find SOMETHING that disagrees with the SM, or there will be trouble ahead…

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  22. H125 says:

    I feel the Irish Times newspaper gave us the most balanced headline for this ‘discovery’

    ‘God particle’ may or may not exist.

    That headline seems to summarise the situation for me.

    Irish Times

  23. Hi Peter,

    it is a bit too early to voice disappointment that this is “only” a SM-like Higgs boson. After all, we do not have discovery of anything yet. Secondly, we do not know whether it is a Higgs boson – does it have spin zero, can we show it couples according to mass by measuring some relative branching ratios, and is the production cross section the SM one? I agree whole heartedly that we need to break the SM (I have been hoping to do that for nearly 20 years now!) but perhaps we could wait and see what we have here – if anything at all. ;)

    Michael

  24. Anon says:

    @H125, while it may be balanced, I find the terminology “god particle” simply detestable and misleading to the public as to what Physics is all about. As Laplace famously said: “Je n’avais pas besoin de cette hypothese-la.”

  25. Allan says:

    The date element of the link appears to have changed. The new, improved permalink is now:
    Higgs Boson Live Blog: Analysis of the CERN announcement
    Also (for now) is available from the main page.

    A certain kind of statistician might ask “what is the largest bump reversal one would expect in a search of this nature?” The false alarm expectation might have been 3 sigmas, though the variance in this kind of meta statistic is often ludicrously high. In any case, I wasn’t all that impressed by the argument on one of the blogs that we’ve already seen an anomaly nearly as big. That could be normal on the path to discovery.

  26. Peter Woit says:

    Allan,

    Thanks, fixed the link.

  27. ESB says:

    “The LHC really needs to find SOMETHING that disagrees with the SM, or there will be trouble ahead…”

    Excuse me Peter, but if the LHC simply confirms the SM, what phenomena through which experiments, in your opinion, should the next generation of particle colliders study ?

    This is a question which any proponent of higher energy colliders beyond the LHC can be expected to address.

  28. Samuel Prime says:

    I don’t have the time to read those papers to get an answer to this, but do I understand that the evidence so far obtained points to the SM Higgs and/or to a muti-Higgs scenario (where one can have as many as 5 Higgs particles)? (Or perhaps I’m uninformed about the number of Higgs in the Standard Model.)

    Secondly, is the evidence supportive or consistent with non-SM Higgs?

  29. David Summers says:

    Michael,

    Re a Higgs being spin zero.

    if we see a resonance in the photon-photon channel, then we have the indication that some object is decaying to two photons.

    Now there is a theorem (is it Yangs theorem – I forget) that only spin 2 or spin 0 particles can decay to two photons – its impossible for spin 1 to do this.

    So if a resonance is decaying into two photons, is probably spin 0 (e.g. a higgs) – or something totally unknown (spin 2).

    David.

  30. Bernhard says:

    Does anyone know if the seminar was recorded and posted somewhere? The transmission was so crappy I gave up in the middle and would be nice to see it wihout the hiccups.

  31. Anon says:

    Bernhard, isn’t it ironic? It’s the 21st century, and though we still don’t have flying cars, we are quite possibly on the verge of finding the Anderson-Higgs. Yet we cannot manage to broadcast a intelligible public announcement of this magnitude, which 20 years ago might have been done perfectly well by TV signal.

  32. tulpoeid says:

    The phrase “inconclusive, as expected” is not “downbeat”; it’s a very objective description of the results and of what >95% of cern experimentalists think right now (95 is a subjective but rather well-informed number).
    Honestly, if lhc shut down *today*, would you be completely honest with yourself in believing that higgs is there? What’s with the hurry people? Find something else to play with for a few more months and then everything will be fine.

  33. Peter Woit says:

    tulpoeid,

    I think “inconclusive, as expected” would have been a good headline for this past summer’s Higgs results. The latest results deserve something different and better.

  34. Peter Woit says:

    Samuel Prime,

    The evidence presented is still not sufficient to claim discovery of a SM Higgs, although it is consistent with such a thing. It’s also consistent with all sorts of other possible Higgs sectors, especially if they’re not that different than a 125 GeV SM Higgs.

    I’d summarize by saying that until now the experiments were just seeing random haze, but the latest results show something emerging from the haze, in exactly the way you’d expect if there were a 125 GeV SM Higgs. However, this is still a ways from being completely sure there’s something there, a long ways from seeing exactly what it is and whether it matches closely with what the SM says it should look like.

  35. VP says:

    If you look at Philip Gibbs’ “unofficial” combined exclusion plots for both November and December, you see that the 95% CL line (black line) is consistently at the upper edge of the two standard deviation band for the mass range of 115-170 or so GeV. To me it says that there is something at low masses (backgrounds?) we don’t understand. Yes, I know, different channels have different backgrounds but still, there is something funny. Wouldn’t this significantly dilute the statistical significance of any bump/excess? Wouldn’t that explain a higher likelihood of excess events in several channels?
    http://blog.vixra.org/2011/12/13/the-higgs-boson-live-from-cern

  36. mp says:

    I am confused as to why everyone is hoping for physics beyond the SM. Why isn’t it good enough for the LHC to confirm the SM?

    Is this purely a funding argument?
    A, more fun, argument?

  37. Peter Woit says:

    VP,

    I don’t think one can take seriously 1-2 sigma size deviations from expectations. Having systematic problems of this size in the understanding of backgrounds wouldn’t be unusual at all. That’s why you don’t start talking about “evidence” until you get to 3 sigma.

    mp,

    There’s a list (fairly short) of ways in which the SM is unsatisfactory. To my mind the most important one is that it’s incomplete: there’s a list of questions you would expect a fundamental theory to answer which it doesn’t (e.g. what determines the different values of the masses and mixing angles of elementary particles?). People who chose to work in HEP are rarely doing it for the money, more likely because they want to know the answer to such questions. Having an experimental result inconsistent with the SM would help a lot to give a hint as to where to look for an improvement of the SM. Without this, you can consistently take the attitude that the SM, incomplete though it may be, is the end of the story. The multiverse is often used to try and provide an intellectual underpinning for this, but, looking at the history of our increasing understanding of fundamental physics, I don’t see a good reason to believe that this pattern of progress has to stop here.

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  39. Damasceno says:

    From a live chat in Nature.com happening now.

    4:22 Gordon Kane: Recently we have published string theory calculations that imply the higgs boson mass is 125 GeV so if it is there are strong implications for connecting string theory to the real world, and for what the higgs discovery implies. we did that before the data.

    Any surprise in the comment?

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  41. Peter Woit says:

    Damasceno,

    The Kane hype is just completely outrageous. I wrote about the source of it in the previous posting

    http://www.math.columbia.edu/~woit/wordpress/?p=4262

    and just added his comments from the Nature chat as an update.

  42. Peter Woit says:

    By the way, Science magazine tomorrow is running a similar live chat, this one with Rob Roser and Kane, see

    http://news.sciencemag.org/sciencenow/2011/12/live-chat-the-higgs-boson-at-las.html?ref=hp

  43. mp says:

    Well obvious I didn’t mean “let’s stop doing science because we confirmed the SM”.

    There are all kinds of unknowns in the SM that need to be figured out. In fact I believe there are decades worth of work ahead of us and strengthening our understanding of the SM and filling in the gaps sounds like pretty serious work.

    I get that it would be more rewarding to find the next revolution for some physicists however not at all costs (I am talking to you string, multiverse, SUSY etc). I believe there should be a healthy balance between speculative and experimental science.

  44. jdm says:

    Peter,

    First, thanks for making your reactions available. They’re quite helpful in clarifying the implications for those of us who aren’t in the loop.

    Now, a nitpick: I don’t believe mp was implying that high energy physicists are “in it for the money,” but rather that the large-scale governmental/inter-governmental support that keeps very-high-energy physics chugging along would be seriously imperiled by a result that has long been touted as the missing piece in an almost complete theory (which appears to be the essence of your reply to anon, Low Math, and Meekly Interacting). This would seem to me to be a powerful and legitimate motivation for wanting to see the SM fail, and one not at all incompatible with equally legitimate intellectual factors you listed.

    Presuming (however prematurely) that an SM Higgs is what CMS and ATLAS are seeing, that funding question would seem to me to loom large over physicists reactions to the results. I would even argue that the proximity of such funding questions probably has a chilling effect on the reception of “standard” results, which might otherwise generate the same kind of excitement the top quark did, despite some dissatisfaction with the SM as it stands.


    -jdm

  45. Samuel Prime says:

    Thanks for your response, Peter.

  46. Peter Woit says:

    jdm,

    Actually my impression is that things are the other way around. The people who run CERN (and have to be very concerned about their funding if they want to stay in business) have been worrying about not finding a Higgs. The worry is that the public and government officials deciding on funding would think: “these guys have been saying for years that they’re spending all this money to find the Higgs, now it turns out they can’t find it. Why should we give them any more money?” Once there’s 5 sigma significance for a Higgs, I’m sure CERN will be appropriately and justifiably crowing about the discovery. Partly because they want the money sources to think of them as a success worthy of future support, but also because, well, they are a success and deserve to be proud such an achievement.

  47. jdm says:

    Peter,

    Interesting. Thanks for that insight. Within the CERN context that makes a lot of sense. I’d still be surprised though if others, particularly in the United States, didn’t look upon a no strings attached Standard Model result as reason to worry over the prospect of securing future funding, especially in the longer term. At any rate, it will be interesting to watch those dynamics as the play out.


    -jdm

  48. Z says:

    There are still plenty of mysteries in HEP, like the anomalous magnetic moment of the muon, neutrino oscillations, dark matter, QCD in general…
    The LHC will probably be funded for the next 15 years, if not longer. The ILC may be superseded by a muon collider design for the future, since a muon collider may be cheaper with existing infrastructure.

    If nothing mysterious is found with the decades-long LHC run in the GeV/TeV sector, HE astrophysics may benefit since Chrenkov telescopes and space telescopes routinely see remnants of particles with energies several orders of magnitude higher than the LHC produces – and thus, they would be the only hope for seeing something beyond the SM. An grand-observatory class X-ray telescope studying neutron stars could also highly constraint QCD equations of state.

  49. VP says:

    Peter,
    “I don’t think one can take seriously 1-2 sigma size deviations…..”

    Perhaps I didn’t make myself clear enough. My point is that if I consistently measure something at 2 standard deviations above the “no Higgs” hypothesis , then an one SD fluctuation would appear as a 3 SD effect. As appears in Gibbs’ plots the measurements of both experiments for the mass range ~115-170 GeV are consistently 2 or so SD above the “no Higgs” hypothesis.

  50. Peter Woit says:

    VP,

    In my reading of the plot, I don’t see “consistently 2 sigma” excess, maybe 1-1.5 sigma. In any case, it looks to me like whatever is locally happening around 125 GeV is 1-2 sigma above other fluctuations and systematic effects. So, 68-95% chance it’s real. I like Jester’s rough guess of 80% (which takes into account the sort of thing this is: looking for something we have reason to expect to be there, not something that shouldn’t be there). One thing that definitely is true is that this is not a genuine 3 sigma effect, in the sense of a 99.7% sure-thing.