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LHC Homes In On Possible Higgs Boson Around 126GeV

Posted by timothy on 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."

12 of 210 comments (clear)

  1. No they can't by AdrianKemp · · Score: 4, Informative

    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.

    1. Re:No they can't by geekoid · · Score: 3, Informative

      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.

      --
      The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
    2. Re:No they can't by rasmusbr · · Score: 4, Informative

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

    3. Re:No they can't by AdrianKemp · · Score: 5, Informative

      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)

    4. Re:No they can't by vikingpower · · Score: 3, Informative

      Both of you are not exactly wrong, nor are you exactly right IMHO. As you guy talk about existence and non-existence proofs ( there are other types of proof ), let me jump on your bandwaggon: Proving negatives sometimes *is* possible, e.g. in mathematics, as in : "There exists no natural number n satisfying such and such properties...". Proving the non-existence of the Higgs Boson is another and much stronger cup of tea. First, the proof domain would be physics, not mere and pure mathematics. Second, the Higgs Boson is a construct within a theory. Proving the HB not to exist would require the theory to be falsified, the outlook for which is, gently said, scant. Third, the mathematics under the theory is sound, provenly so. Therefore, both of you are ( not so exactly ) wrong.

      --
      Religous speak to God. Insane are spoken to by God. When all shut up, one can finally hear Shostakovich in peace
  2. I for one welcome our Higgsy overlord... by TenDollarMan · · Score: 5, Informative

    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.

    --
    I hate my flatmate
  3. Re:How do they calculate the upper bound? by fljmayer · · Score: 5, Informative

    As said at http://cms.web.cern.ch/news/cms-search-standard-model-higgs-boson-lhc-data-2010-and-2011, they have excluded 128 – 525 GeV at 99% confidence level. I am not sure they measure higher than 525 GeV with LHC for now. I would expect that existing theories for the Higgs put limits on its mass. Of course theories can be wrong, but if all theories about the Higgs are wrong, then there is no such particle.

  4. Re:Who gets their name written in the history book by rubycodez · · Score: 3, Informative

    uh, you do know "Higgs" is a physicist's name? http://en.wikipedia.org/wiki/Peter_Higgs

  5. Re:How do they calculate the upper bound? by kkumer · · Score: 5, Informative

    Looking for higher mass Higgs is easier than for this 120-ish GeV mass. E.g. if Higgs would be 150-200 GeV it would (via heavy vector bosons, which are 80-90 GeV) decay a lot into electrons and muons which are very easy to detect and see that they come from decay of Higgs. For 120-ish GeV Higgs, it decays mostly into two quarks and this is difficult to see because there are a *lot* of quarks flying around in proton-proton machine. So they have to use decays into two photons, which don't happen so often. Thus they need more time to discover Higgs of 125 GeV, than they would need for the one of 200 GeV.

  6. Yes we can! by Roger+W+Moore · · Score: 5, Informative

    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.

    1. Re:Yes we can! by Anonymous Coward · · Score: 2, Informative

      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.

  7. Re:If I understood it correctly by jfengel · · Score: 4, Informative

    There's also a dog-that-didn't-bark factor here. If the Higgs didn't exist at all, that absence would have manifested itself in this data. They still can't give the mass, but there was an opportunity for the data to surprise us, and it didn't. Which just means more looking, as opposed to going all the way back to the drawing board.