Higgs boson semantic questions

  1. The first question is why it is sometimes called the "Higgs meson"?-even by its discoverers, see recent controversy about the particle's name and the proposal to call it "standard model scalar meson", isn't a meson a composite particle while the particle detected by the LHC supposed to be elementary?, (abstracting for a moment from the theoretical expectations) isn't it experimentally easy to tell that what Atlas and CMS detected is composite or elementary?

    The second question is whether there is a clear reason (again looking more at the empirical observation than to the theoretical expectation) in the observed peak by Atlas and CMS to call it (resonance)particle over resonant state?
  2. jcsd
  3. Vanadium 50

    Vanadium 50 17,329
    Staff Emeritus
    Science Advisor
    Gold Member

    It's not. Please provide a citation.
  4. That's just a through back to older nomenclature. The meaning of the word meson has evolved overtime (even the muon was at some point considered a meson.)
  5. You are right dauto, apparently the references I looked (one by Higgs himself -My life as a boson:the story of 'the Higgs' -) that refer to "Higgs meson" are either historical or refer to alternative Higgs like that of Technicolor.

    But the discussion about the name and who should be awarded with the nobel is recent, and according to media reports Hagen said when asked What would he call it: “The standard model scalar meson. Then you could call it SM-squared.”
    I guess it was a joke.
    Anyway I'm curious how would the decay rates, etc would differ if what was detected instead of an elementary particle was some exotic scalar meson outside the standard model?

    How about my second question?
  6. I'm not sure I understand you second question. Can you restate it?
  7. Bill_K

    Bill_K 4,160
    Science Advisor

    Whether or not the Higgs boson is elementary, and how to tell, has been much discussed. Googling "composite Higgs" will get you half a million hits. Generally speaking, a composite Higgs implies a deeper, as yet undiscovered, level of strong interactions. One might hope this would lead to additional exotic particles within the LHC's reach.

    But if the Higgs is all we have to work with, we'll look closely at its couplings. For a composite Higgs we'd expect its couplings to decrease with increasing energy, similar to the way the electromagnetic form factors for baryons fall off, telling us that they're made of quarks.

    Of particular importance is the hWW coupling in W-W scattering. The standard value of this coupling suffices to preserve unitarity in WW scattering in the high energy limit. But if the Higgs is composite, it won't, and something else must eventually take its place.
  8. Thanks for the informative answer.

    Just wondering if the observed peak can be considered as a resonant state rather than as such a short-lived particle given that supposedly in QFT the quantum fields are the fundamental entities rather than the ill-defined "particles" (that are just the excited states).
  9. mfb

    Staff: Mentor

    It is a particle with a small decay width (too small to be seen by experiments, <2 GeV, with a prediction of a few MeV).

    Compared to resonances, it is "long-living".
  10. Higgs mean lifetime as predicted by the SM is in the order of 1.56*10^-22 seconds while resonances are supposed to be in the order of 10^-23 seconds according to this web page http://www.phy.duke.edu/~kolena/modern/dudley.html that also shows the distinction I'm highlighting between resonances as particles vs excited states associated to the scattering experiment energies and cross sections.
  11. K^2

    K^2 2,470
    Science Advisor

    Higgs boson has quantum numbers compatible with certain meson excitations. So it'd be entirely possible, initially, for a meson of some sort to be mistaken for a Higgs boson. By now, the possibility of what they found being a meson has been thoroughly excluded.
  12. Bill_K

    Bill_K 4,160
    Science Advisor

    No, there was never a stage where the particle seen at 126 GeV could have been "just another meson". One of the primary decay channels was h → ZZ → μμμμ, (see attachment, μ's are in red) showing that the particle had a deep connection to the weak interaction. But it could have been something more exotic than the standard Higgs, and for this reason it was early-on called "Higgs-like".

    Chief among these would be its spin and parity, which are at present only partially confirmed.

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    Last edited: Nov 4, 2013
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: higgs boson