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Do you believe the Higgs boson was experimentally confirmed?

  1. Jun 3, 2015 #1
    Do you believe the Higgs boson was already experimentally confirmed?

    I guess that, as with any elementary particle, the Higgs boson should have a lot of theoretical properties that must all be experimentally confirmed to be sure it is Higgs' and not some other entity. Have the scientists experimentally found all these properties?
     
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  3. Jun 3, 2015 #2

    mfb

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    This is not a matter of belief.
    All measurements so far (more than 50 papers with even more measurements) agree with theory predictions. It is either exactly the predicted particle or something so extremely close that we would still call it "Higgs boson".
    There are predictions that will take much more data to check, but there is no reason to assume that the Higgs shows deviations exactly there and nowhere else.
     
  4. Jun 3, 2015 #3
    For example, what are the properties that have already been experimentally confirmed?

    This March 2015 article (http://news.discovery.com/space/the-higgs-boson-may-disintegrate-into-dark-matter-150203.htm) says that the Higgs boson was just indirectly detected:
    "The LHC’s detectors didn’t directly ‘see’ a Higgs boson when it made its discovery. The ATLAS and CMS detectors, over countless billions of particle collisions, slowly built up a picture of post-collision particles that sprayed away from the energy generated after counter-rotating protons smashed into one another. From this collision energy, Higgs boson particles condensed in isolation but rapidly decayed into other particles that the detectors could measure, such as muons (the electron’s more massive cousin). This provided a Higgs ‘fingerprint’ of sorts, evidence that Higgs bosons are being generated."
     
    Last edited: Jun 3, 2015
  5. Jun 3, 2015 #4

    Orodruin

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    Couplings to other particles, spin, and parity to name a few. "If it walks like a Higgs and quacks like a Higgs" ...
     
  6. Jun 3, 2015 #5
    "The standard model also predicts that the Higgs field couples to fermions through a Yukawa interaction, giving rise to the masses of quarks and leptons. The structure of the Yukawa interaction is such that the coupling strength between the standard model Higgs boson and a fermion is proportional to the mass of that fermion. As the masses of many quarks and leptons are sufficiently well known from experiment, it is possible within the standard model to accurately predict the Higgs boson decay rates to these fermions. The existence of such decays and the corresponding rates remain to be established and measured by experiment. Indirect evidence for the Higgs coupling to the top quark, an up-type quark and the heaviest elementary particle known to date, is implied by an overall agreement of the gluon–gluon fusion production channel cross-section with the standard model prediction. However, the masses of down-type fermions may come about through different mechanisms in theories beyond the standard model. Therefore, it is imperative to observe the direct decay of this new particle to down-type fermions to firmly establish its nature."
    See: http://www.nature.com/nphys/journal/v10/n8/full/nphys3005.html
     
  7. Jun 3, 2015 #6

    mfb

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    Yes, in the same way the sun is just "indirectly detected" - no one ever touched it, but we see its radiation and other effects and we are highly confident the sun exists.
    This is the introduction. They write it exactly because they did measure it.

    The decays to tau and b-quarks have been seen. Not as precise as the measurements of the decay to bosons, but it has been found. The others are predicted to be so rare (or hard to find) that a clear discovery would be in conflict with theory. The non-discovery so far is perfectly in agreement with predictions.
     
  8. Jun 3, 2015 #7

    ZapperZ

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    So me an example of what YOU would consider as a "direct" detection.

    Zz.
     
  9. Jun 3, 2015 #8
    The Sun is directly detected as any object you can see with your own eyes. Do not come with philosophies like this because they are outdated. If we doubt everything we see we go back in the time of Greek philosophers.
     
  10. Jun 3, 2015 #9

    ZapperZ

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    No you don't.

    You detect the light and other radiation coming from the sun. I could also detect the solar neutrinos, the gravitational field, etc. in other words, I detect the PROPERTIES that we associate with what we call the "sun"! This is not philosophy. This is what we mean in physics when we verify the existence of something, via a collection of its properties!

    Would like to compare this idea again with what we detect for the Higgs?

    Zz.
     
  11. Jun 3, 2015 #10
    A direct detection in the case of an elementary particle would be the confirmation of all its known theoretical properties in such a way that no counterargument can be found.

    This Physical Review article (http://www.iflscience.com/physics/more-colorful-higgs) rises serious doubts about the existence of the 125 GeV Higgs boson.

    "The authors argue that it is possible the resonance found at 125 GeV is a “technicolor (TC) isosinglet scalar, the TC Higgs.” Among the competing models of the universe, many predicted the Higgs with a mass in a range that included 125 GeV, where the particle was found. However, in certain models, known as technicolor, the Higgs is likely to have a higher mass, and another particle, known as the TC Higgs or techni-higgs would exist around this level.

    Though they sound similar, the techni-higgs is quite different.

    "A techni-higgs particle is not an elementary particle.
    "
    Source: http://www.iflscience.com/physics/more-colorful-higgs
     
  12. Jun 3, 2015 #11

    mfb

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    You can always - literally always! - find some model that gives something very similar to your particle, but slightly different. Those models need more and more unrealistic fine-tuning the more precise and numerous measurements become.

    What is the purpose of this thread? If you want to learn something about the Higgs - fine, ask questions. If you want to suggest ATLAS and CMS would have done a bad job, this is the wrong place.
     
  13. Jun 3, 2015 #12

    ZapperZ

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    But this is a separate issue than your claim of a more "direct" detection! To verify the Higgs proposed in this paper, we will be doing the SAME type of detection that you called as "indirect"! Would you buy it then?

    Read my earlier rebuttal of what you claim as a direct detection of the sun.

    Zz.
     
  14. Jun 3, 2015 #13
    Basically you tell me that we have to doubt the existence of all objects we see around us but we can not touch. Judging like this we can equally doubt the existence of all things we can touch but we can not see (because they are in a dark room for instance). This is pure philosophy not physics.
     
  15. Jun 3, 2015 #14

    mfb

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    No, you seem to be suggesting this with the comment about "indirect" detection.
     
  16. Jun 3, 2015 #15

    ZapperZ

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    No, you are doubting it. I don't! At some level, the evidence is convincing enough!

    Are you convince of the existence of x-Rays even though you can't see it? And "touching" as a "detector" to judge if something exists or not is very poor and unreliable, and so is seeing it with your eyes.

    I'm an experimentalist. It is part of my overall job to measure the properties of many things. And this is why I claim that everything that we claim to know to exist is based on our verification of a set of properties. You complaint that the Higgs wasn't detected directly is an empty claim, because it is as legitimate as any other detection that you THINK is direct.

    Go back and consider all the things that you think you know of. Look at an apple. The way you know what it is is based entirely on it properties. That is what defined what it is. How is this any different than what we have measured of the Higgs?

    Zz.
     
  17. Jun 3, 2015 #16

    PeterDonis

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