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Science

LHC Homes In On Possible Higgs Boson Around 126GeV 210

Posted by timothy from the abundance-of-caution dept.
New submitter Ginger Unicorn writes "In a seminar held at CERN today, the ATLAS and CMS experiments presented the status of their searches for the Standard Model Higgs boson. Their results are based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs. The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery."
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LHC Homes In On Possible Higgs Boson Around 126GeV More

LHC Homes In On Possible Higgs Boson Around 126GeV

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  • No they can't (Score:5, Informative)

    by AdrianKemp ( 1988748 ) on Tuesday December 13, 2011 @11:05AM (#38355988)

    Unless things have changed since yesterday, the LHC cannot disprove the HB.

    It can show that it isn't within certain energy ranges, but it does not have the capability of emphatically disproving it's existence over the entire predicted spectrum.

    • Re: (Score:3, Informative)

      by geekoid ( 135745 )

      It has to appear withing a certain range. Check all the ranges.

      Obviously, new data could have adjust those ranges, but no new data or math has come forward.

      It's like checking to see if a car in in a garage by looking at 1 sqr. mete at a time. eventual you will show that there is, or is not, a car in the garage.

      • Re:No they can't (Score:5, Informative)

        by AdrianKemp ( 1988748 ) on Tuesday December 13, 2011 @11:20AM (#38356210)

        No that's the point; they can't check all the ranges.

        The LHC is incapable of operating at the upper energies of the predicted spectrum of the higgs boson. It simply cannot check all of the places it might be hiding (this was known before construction even started)

        • Re:No they can't (Score:4, Funny)

          by geekoid ( 135745 ) <{moc.oohay} {ta} {dnaltropnidad}> on Tuesday December 13, 2011 @11:24AM (#38356260) Homepage Journal

          And that is why I shouldn't post until I have completely woken up. I mean, you clarified it in your second sentence.

          Sheeesh. Sorry about that.

        • Yes we can! (Score:5, Informative)

          by Roger W Moore ( 538166 ) on Tuesday December 13, 2011 @12:10PM (#38356870) Journal

          The LHC is incapable of operating at the upper energies of the predicted spectrum of the higgs boson.....(this was known before construction even started)

          Sorry but we certainly are capable of probing the ENTIRE allowed mass range for the Standard Model Higgs. The upper bound is ~1 TeV/c2 because at this level, without the Higgs boson, some Standard Model processes e.g. e+e--->W+W- "break unitarity" i.e. have a more than 100% chance of happening. Since this is clearly wrong it means that the Standard Model without a Higgs breaks down. Hence we only have to cover up to 1 TeV/c2 in allowed mass and either we find the Higgs or at least see a clear deviation from the SM and possibly see what causes that deviation.

          There are ways to hide the Higgs, so-called "invisible Higgs" models, but these all require physics beyond the Standard Model. Also you can fit the existing SM parameters to find a prediction for the Higgs mass and this indicates that it should be below ~200GeV/c2 with a 95% confidence - although I'd take this with a pinch of salt. Now to get to the high mass range we will certainly need the full LHC energy i.e. 14 TeV. We currently have 7 TeV but this is NOT what the LHC was designed to run at - we are just limited to this energy due to the superconducting power bar problems. So to say that it was known that we cannot reach the upper energies before construction even started is simply wrong - the LHC was specifically designed to cover the entire energy range and, once we reach the design energy, we'll be able to do just that....although it is looking like the Higgs is there just at the low end of the mass range.

          • Comment removed (Score:5, Funny)

            by account_deleted ( 4530225 ) on Tuesday December 13, 2011 @12:34PM (#38357148)
            Comment removed based on user account deletion

          • It's certainly possible that I've missed a development over the years... However, the predictions you speak of rely on two (that I'll cover) very important things:

            The standard model being correct
            There being no other "fudge" particles discovered along with the Higgs that rectify the breaks

            Assuming that the LHC shows no higgs below 200GeV (I think it's now excluded above 150) and can also show no other "fudge" particles across all possible ranges for them to exist; they have disproven the standard model.

            That

            • Re: (Score:2, Informative)

              by Anonymous Coward

              Both the summary and grandparent talked about the Standard Model Higgs, not any abitrairy Higgs Particle. The assumptions you point out are inherent in the definition of the Standard Model Higgs. It is a subset of the possible Higgs particles that could exist, and has the nice properties of being the simplest possible and also being possible to disprove with the LHC.

            • The standard model being correct

              You'll note that I was very careful to call it "the Standard Model Higgs". If there is. e.g. Supersymmetry, then things can be different....but something still has to happen before 1 TeV. So you can disprove the Standard Model Higgs boson but not all Higgs bosons. However if you find that nature solves the mass problem in a different way then there would be no need for a Higgs boson.

              • Yes and I was overly argumentative with you because the CERN stuff was very ambiguous in places about which they were talking (you really weren't, so you have my apologies on that front).

          • Yes its the invisible, or the mixtures between invisible and visible Higgs, that are the most exciting, because these are the ones that lead to the detection of Dark Matter or Mirror Matter [blogspot.com], particles.

          • Re:Yes we can! (Score:4, Interesting)

            by hweimer ( 709734 ) on Tuesday December 13, 2011 @03:10PM (#38359946) Homepage

            Sorry but we certainly are capable of probing the ENTIRE allowed mass range for the Standard Model Higgs. The upper bound is ~1 TeV/c2 because at this level, without the Higgs boson, some Standard Model processes e.g. e+e--->W+W- "break unitarity" i.e. have a more than 100% chance of happening.

            I somehow never got this point. In the standard model, you're starting from a Lagrangian formulation of a quantum field theory, so the existence of a scalar product in the Hilbert space spanned by the theory automatically guarantees normalization of probabilities, no matter which physical values you attach to the parameters of your model. So if you're getting something larger than one, you must have made an error somewhere on the way, but that doesn't imply your entire model is wrong.

            • Re:Yes we can! (Score:4, Interesting)

              by Roger W Moore ( 538166 ) on Tuesday December 13, 2011 @06:34PM (#38363596) Journal
              If you assume no Higgs then you end up with a Lagrangian without any mass terms (because if you put those in you break the local gauge symmetries). However when you do the calculation of e.g. e+e- --> W+W- you have to use the fact that the electron has a mass in the Feynman calculation. This non-zero mass causes you you have a "left over" term which does not cancel in the high energy limit and causes you to break unitarity.

              The Higgs mechanism gets around this by adding a new diagram e+e- --> H --> W+W- which precisely cancels the electron mass term. The reason the cancellation is perfect is because the electron gets its mass from coupling to the non-zero Higgs vacuum expectation value.

              So effectively you are correct in that the reason the model fails at high energy is because you use the electron mass in the cross-section calculation but have no electron mass term in the Lagrangian so you are not being consistent....but you cannot simply stick a mass term in there without adding symmetry breaking interactions which are not observed in nature. Hence you have to add a Higgs field with a non-zero vacuum expectation value which in turn adds more than just the effective mass terms.

              Hope that is comprehensible - it is hard to explain in just typed text!
        • Thats incorrect, physicist know that there must have been some like the Higgs below 1TeV, and the LHC runs at 7 TeV, soon to be 14 GeV. Even with those 7 TeV divided into 3, (its the quarks that interact not the whole proton, actual its 3+3*(1+1/alpha_strong+1/apha_strong^2...Higher terms), because of the gluons in the proton). But the interaction energy is about 2 TeV per quark, so the LHC can look for a Higgs all the way to 2 Tev, evidential 4 TeV.

          ---

          Particles Physics [feeddistiller.com] Feed @ Feed Distiller [feeddistiller.com]

          • I replied in more detail to the poster above you, but it boils down to this:

            Disproving the standard model is not disproving the higgs boson (so to speak).

            The photon is a member of the standard model too, but it doesn't mean that if they disprove the standard model photons cease to exist.

            Once they have covered all theoretical ranges of the higgs boson including the ones that allow for breakage of the standard model, then they will have disproven the HB

    • Re:No they can't (Score:5, Informative)

      by rasmusbr ( 2186518 ) on Tuesday December 13, 2011 @11:09AM (#38356044)

      They didn't make any specific claims today, except that there's an energy region that looks quite promising. Read the official press release [web.cern.ch]

      • I did, and it specifically mentions a confirmation of existence or non-existence in 2012.

        If they meant non-existence within a specific energy band, fine but that isn't what they said in the release.

        • I must have misread your post. I thought you meant that the data gathered so far by the LHC can't disprove the existence of the Higgs boson.

          So you mean that the LHC is unable to disprove all of the Higgs bosons that have been proposed? That's interesting. Do you have a link to an article about that for the non-physicists among us?

        • If they meant non-existence within a specific energy band, fine but that isn't what they said in the release.

          The Standard Model Higgs is constrained to lie within a particular energy band due to certain scattering processes becoming more than 100% likely to occur around 1 TeV/c2 if there is no Higgs (or something else). I have not seen our ATLAS predictions for the reach with twice the 2011 data (which is what we expect in 2012) but I would be surprised if it is enough to exclude all the way to 1 TeV/c2. However if it occurs at the top end of the mass range, then it becomes hard to reconcile with the existing Sta

      • Re: (Score:2)

        by mcgrew ( 92797 ) *

        Well, since the war is over [nytimes.com] it won't be long before they find the Higgs. [slashdot.org]

    • Unless things have changed since yesterday, the LHC cannot disprove the HB.

      The article/summary is over simplified. They are trying to prove or disprove the standard model. It predicts the existence of the Higgs boson within a certain energy range. Failure to find the Higgs boson within those ranges will disprove the standard model.

      • Re: (Score:3)

        by Old Wolf ( 56093 )

        The standard model seems to be fairly slippery anyway.

        The SM predicts that neutrinos have no mass, but experiments show that they do. However, physicists do not seem to say that this disproves the SM. The feeling is more that the SM could be adjusted so that it features neutrinos with mass.

        Something similar will probably happen if there is no Higgs Boson found in the expected area. One of the hundreds of SM variants that are floating around, which happens to not include a HB in that area, would gain p

    • They could if the data suggested it.

      As it is, the data strongly indicates the Higgs is in fact around 120 GeV, but they only have enough statistics so far to claim "evidence" and not "proof".

    • Re:No they can't (Score:4)

      by bcrowell ( 177657 ) on Tuesday December 13, 2011 @12:41PM (#38357270) Homepage

      Unless things have changed since yesterday, the LHC cannot disprove the HB. It can show that it isn't within certain energy ranges, but it does not have the capability of emphatically disproving it's existence over the entire predicted spectrum.

      That's literally true but misleading. Here [arxiv.org] is a paper that explains how non-LHC data constrain the standard-model Higgs to have a mass between 115 and 148 GeV. The LHC can't test whether there's a Higgs with a very high mass, but that's irrelevant because we know it has to be below 148 GeV based on non-LHC data. Based on the combination of non-LHC and LHC data, we know that if there's a standard-model Higgs, then it has a mass of about 115-127 GeV. The LHC is absolutely capable of disproving the existence of a standard-model Higgs within that mass range, if it doesn't actually exist. If there is no SM Higgs, we will know that within a couple of years based on LHC data.

      The real reason there may be a lot of uncertainty for years to come is that there are many different ways of making a model with a Higgs in it. The standard model is only one of them. Some of the non-SM Higgses could be very difficult to detect. Here [profmattstrassler.com] is a nice discussion of that. There are scenarios where the SM Higgs is ruled out by 2014, but by 2022 we still will not have detected or ruled out a non-SM Higgs.

      • I've looked at it again, and I think the issue is in their wording. They flip back and forth between saying "Standard Model Higgs Boson" and just Higgs Boson.

        Those are very different things, and if you assume that they mean SM everywhere they don't say it then what they say is valid.

        They will not ever be able to disprove the Higgs Boson with the LHC, disproving the standard model (higgs boson) isn't an issue.

    • Re: (Score:2)

      by JamesP ( 688957 )

      Erm... no

      Actually, the LHC can't prove the existence of the Higgs Boson

      They can show overwhelming evidence for it, up to the point the Higgs Boson is as accepted as the electron for instance

      But until then, you can't "disprove" a thing that has the best evidence for existing @ 3 sigma...

      • Try replying to what is actually written next time.

        Nobody will *ever* be able to prove the existence of the higgs boson. LHC cannot *disprove* the existence of the higgs boson.

        Those statements do not contradict each other, and I only made one of them.

        Thanks for playing though

        • Re: (Score:2)

          by JamesP ( 688957 )

          You can't disprove the existence of something which is not sure to exist.

          (Of course, you can't turn off a light that's already off, but that's too obvious)

          So saying the LHC cannot disprove the HB is like saying no one can disprove Unicorns

          nice try

    • I can emphatically say the Higgs boson does not exist.

      However, me being emphatic does not have any significance.

      Hence, the the probability of the Higgs boson existence is greater-than or equivalent-too the significance of my emphatic comment.

      Reality is self-induced hallucination.

  • So far, so good (Score:5, Funny)

    by vlm ( 69642 ) on Tuesday December 13, 2011 @11:08AM (#38356028)

    So far, so good, no one here calling it the God Particle yet. Lets keep it that way. Annoying as all hell.

    http://en.wikipedia.org/wiki/Higgs_boson#.22The_God_particle.22 [wikipedia.org]

    "Lederman initially wanted to call it the "goddamn particle," but his editor would not let him"

  • Just out of curiosity, how exactly do they constrain the upper bound on the mass of the Higgs boson? I mean, the lower bound seems to be "we've looked at that energy level and it probably isn't there", but they can't do that for the upper bound, can they?

  • The Higgs Boson (Score:5, Funny)

    by philj ( 13777 ) on Tuesday December 13, 2011 @11:10AM (#38356064)
    The Higgs Boson is holding a press conference at midnight on Dec 24th. He's giving Christmas mass.

  • I for one welcome our Higgsy overlord... (Score:5, Informative)

    by TenDollarMan ( 1307733 ) on Tuesday December 13, 2011 @11:11AM (#38356074) Homepage

    I was lucky enough to have a lunch hour where I could see the ATLAS results presentation.

    The actual bump on the ATLAS graph was about 126 GeV, and the local sigma was 3.6 which is pretty good. The overall was only 2.4, which IIRC is about 95% certainty. I like the odds of finding it there.

    • Re:I for one welcome our Higgsy overlord... (Score:5, Interesting)

      by bill_mcgonigle ( 4333 ) * on Tuesday December 13, 2011 @01:03PM (#38357586) Homepage Journal

      The actual bump on the ATLAS graph was about 126 GeV, and the local sigma was 3.6 which is pretty good

      This model of everything [arxiv.org] predicted a Higgs at 125.992, which is pretty close (with the current error bars). Could be coincidence, of course, but their idea of a well-defined set of rules that predicts each particle's mass correctly is tantalizing.

      • Re: (Score:2)

        by Troed ( 102527 )

        "We show that the mathematical proof of the four color theorem yields a perfect interpretation of the Standard Model of particle physics. [...] giving us a Grand Unified Theory." [---] "we present our prediction of the Higgs boson mass = 125.992 GeV, as a direct consequence of the proof of the four color theorem." (2009-12-28)

        Thanks for the link, I really enjoyed their approach.

  • If I understood it correctly (Score:5, Insightful)

    by marcosdumay ( 620877 ) <(marcosdumay) (at) (gmail.com)> on Tuesday December 13, 2011 @11:23AM (#38356252) Homepage Journal

    The announcement today just narrows the mass. The /. summary is perfectly adequate, and is a complete summary of the situation!

    There is also a small point, about a candidate mass just under 127GeV, with less than 3 sigma. The /. title is talking about that, but doesn't clarify it. Of course, some information with less than 3 sigma can change any time.

  • May We Live in Interesting Times. (Score:5, Insightful)

    by Remus Shepherd ( 32833 ) <remus@panix.com> on Tuesday December 13, 2011 @11:34AM (#38356418) Homepage

    The fascinating thing about the energy they're talking about (125-126 GeV) is that it's too low. So low, in fact, that the equations predict vacuum instability at about that range. [vixra.org]

    What does vacuum instability mean? It means that vacuum might have a half-life, after which it decays into energy. This is a cool concept until you realize that the Universe is mostly made of vacuum. If the Universe were to spontaneously disintegrate, that would be Bad.

    Of course since that doesn't happen, there must be new physics that keeps everything from fizzling out. That means that if the Higgs boson is found at 126 GeV then we're not done searching. There will be new questions to answer and possibly a new particle, the Higgsino [wikipedia.org], to look for.

    Exciting stuff if you're a physics nerd. Or really for anyone who has a vested interest in the Universe continuing to exist.

    • Re: (Score:2)

      by ledow ( 319597 )

      "There's always an Alien Battle Cruiser...or a Korlian Death Ray, or...an intergalactic plague about to wipe out life on this planet, and the only thing that lets people get on with their hopeful little lives is that they don't know about it."

      I wouldn't be worried about vacuum instability as a cause of death, I'd be more interested in it as an energy source, personally. But then we're still talking huge amounts of pie-in-the-sky concepts here.

    • I don't understand why everybody seems to have a problem with vacuum instability. Ok, not with instability per se, but what is the problem with meta-stability? Wouldn't it explain inflation?

      • Re:May We Live in Interesting Times. (Score:5, Interesting)

        by Remus Shepherd ( 32833 ) <remus@panix.com> on Tuesday December 13, 2011 @12:28PM (#38357062) Homepage

        Metastability might explain inflation. But it also invites the possibility that inflation could kick off again, and the universe could revert to a previous state where things like stars, planets, and life can not exist. That's what people have a problem with, I think.

        Of course, the fact that this hasn't happened is proof that it probably cannot. The question we then need to answer is why not. It's as if God has us all in a gigantic microwave oven, and we're trying to figure out what's keeping him from hitting the 'Start' button...

        • Re:May We Live in Interesting Times. (Score:5, Funny)

          by Translation Error ( 1176675 ) on Tuesday December 13, 2011 @01:53PM (#38358418)

          It's as if God has us all in a gigantic microwave oven, and we're trying to figure out what's keeping him from hitting the 'Start' button...

          It's the tinfoil hats. He's waiting for everyone to take them off so he doesn't scorch the oven.

        • Of course, the fact that this hasn't happened is proof that it probably cannot. The question we then need to answer is why not. It's as if God has us all in a gigantic microwave oven, and we're trying to figure out what's keeping him from hitting the 'Start' button...

          not seen a Hitchhikers Guide quote today so here goes:

          There is a theory which states that if ever anybody discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another theory which states that this has already happened.

    • What does vacuum instability mean? It means that vacuum might have a half-life, after which it decays into energy. This is a cool concept until you realize that the Universe is mostly made of vacuum. If the Universe were to spontaneously disintegrate, that would be Bad.

      Maybe it's a dead man switch in case God dies before his experiment is finished.

    • Re:May We Live in Interesting Times. (Score:4, Insightful)

      by dotancohen ( 1015143 ) on Tuesday December 13, 2011 @01:20PM (#38357876) Homepage

      If the Universe were to spontaneously disintegrate, that would be Bad.

      I'm fuzzy on the whole good/bad thing. What do you mean "bad"?

    • Re:May We Live in Interesting Times. (Score:5, Insightful)

      by mcgrew ( 92797 ) * on Tuesday December 13, 2011 @02:26PM (#38358994) Homepage Journal

      If the Universe were to spontaneously disintegrate, that would be Bad.

      No, I don't think anyone would complain. You have to die from something, the universe spontaneously ceasing to exist probably wouldn't be a bad way to go considering the alternatives (fire, drowning, cancer...)

      Or really for anyone who has a vested interest in the Universe continuing to exist.

      From my perspective it's only existed for 59 years and its destruction is always and has always been imminent. The universe stops existing for people every single day. Nobody has a vested interest in the universe's existance; we're only visitors here. Nobody stays forever.

  • 5.60 Gigawatts! 5.60 GIGAWATTS?! Great Scott!

  • THey should not have held a presser at this point as what they had really wasn't very much at all. Going from memory I think it was 3.6 sigma at Atlas and 2.6 at CMS but when including LEE the Atlas result dropped significantly, something like 1.9 or 2.2? And CMS dropped as well. As DO, CDF and others can attest, 3 and even 4 sigma bumps can and do vanish under increased statistics. And while the p figures for Atlas and CMS were good, I just do not buy into combining the results of weak sigma events to

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      "I just do not buy into combining the results of weak sigma events to claim something more significant."

      Which means you have a poor or at least incomplete understanding of statistics.

      The rest of your comment expresses an opinion about whether science should announce intermediate results, or wait until something is more definite. If you go with the former, the public might be confused because they don't understand that the results are preliminary. If you do the latter, the public might become frustrated wi

    • Re: (Score:2)

      by bware ( 148533 )

      I'd imagine it's done because it's difficult to keep these (preliminary) results quiet nowadays. This news has been buzzing about the internets for weeks. Why not have an announcement saying what's going on? It's not as though it is a big secret anymore, and it forestalls a lot of the speculation.

      More fb^{-1} needed...

  • Sure there are legitimate uses of "home in on" as in a homing missle, but really the verb for this kind of work is really hone - to make more acute, intense, or effective. Homing is more about traveling, honing is about narrowing down. Sure in some degree they are related, but here the intent is narrowing.

    • Re: (Score:2)

      by ceoyoyo ( 59147 )

      Since the experiment is described as a "search", "home in on" is the proper phrase. If you were to use hone, the headline would be confusing and non-specific. "LHC Hones It's Higgs Results" or something.

  • What does this all mean? (Score:4, Funny)

    by ronaldo1 ( 11627 ) on Tuesday December 13, 2011 @01:49PM (#38358344)

    Can we have anti-grav vehicles, plasma swords and powered armor or not?

  • Just nothing. After weeks of enduring "God particle" teasers about a "possible announcement", it all turns out to be nothing conclusive, no announcement of a definite find. I *knew* that would happen, yet still I feel had. This is PR-hype coitus interruptus aimed at driving more funding.

  • We still don't friggin know.

  • Seems more like eliminating (Score:3)

    by BlueCoder ( 223005 ) on Tuesday December 13, 2011 @08:50PM (#38364862)

    Personally I hope they don't find higgs.

    I just don't buy gravity as a particle. They seem to want to reduce everything analog to a particle.

    What I want to see is them quantifying is space as a thing; that the ether is actually a real tangible thing and how it relates to the bubbles in it that we call particles and how these particles are moving in multiple "dimensions" and yet we only really notice 3 of space and 1 of time.

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