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New Particle: X(3872)

  1. Nov 21, 2003 #1
    http://news.bbc.co.uk/2/hi/science/nature/3277579.stm
     
  2. jcsd
  3. Nov 21, 2003 #2

    mathman

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    There were two strong caveats in this story. First, QCD is a difficult theory when it comes to carrying out calculations. Second, the most likely candidate seems to be a four particle (two quark and two antiquark) combination. It seems that a lot more grunt work is necessary before changing the current theory,
     
  4. Nov 22, 2003 #3
    Turns out that if you collide Non-Dimensional entities(e+e-) enough times, then it is more than likely that you will produce a Non-Dimensional molocule?
     
  5. Nov 22, 2003 #4
    i dont agree with any new particle theories.you should read the book, In search of shrodingers cat. the author makes a few VERY good points about sub atomic particles and how we can find ANYTHING we want that will behave the same way everytime we observe it because observations cannot be made in the quantom world without changing what wee observe. Its all about the uncertanty principle.

    "Math my dear boy, is nothing more than the lesbian sister of biology." --Peter Griffin
     
  6. Nov 23, 2003 #5

    Haelfix

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    Yea the author clearly doesn't know what he is talking about.

    The Heisenberg uncertainty principle is at the heart of particle physics, all physical particles obey it.

    All these particles are reproducible, have invariant properties such as charge, flavor, etc that have been tested, and retested in the laboratories to something like .1% margins of error.

    You can't get 'anything in the world', that much is beyond obvious at this stage.
     
  7. Nov 23, 2003 #6

    selfAdjoint

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    I think you may be misremembering what Gribbin said. He sometimes has gone off the deep end, but lately he's been pretty careful to be sound. The uncertainty principle is quite specific, it concerns noncompementary quantum properties and not the existence of observable particles.
     
  8. Nov 23, 2003 #7

    ahrkron

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    This is a strange comment to make. If a theory predicts particles that haven't been found, it is not a matter of agreeing with the theory, but one of going and measure.

    I read the book sometime ago, and don't remember such comment (I think I would remember it). Regardless of my memory, I can assure you that if this were true, the Higgs would have been found a few billion dollars ago.

    I think this goes contrary to the previous assertion that we will find "anything we want", for what happens if tomorrow someone wants to find the opposite of what I found today?
     
  9. Nov 24, 2003 #8
    i was meerly stating my opinion about new particle theroys
    i interprited my readings as i have stated. i CAN agree that my previous post was poorly worded, but i do stand by the sensible parts of what i said.
    in regards to being reproduceable...i think if you run the same tests you will get the same results, interpriting them as a new particle is up to you...

    "Hey, but im only 17, what do i know" --Me
    "Math, my dear boy, is nothing more than the lesbian sister of biology" --Peter Griffin:frown:
     
  10. Nov 24, 2003 #9
    WaveLength wrote:

    > we can find ANYTHING we want that will behave the same way
    > everytime we observe it because observations cannot be made
    > in the quantom world without changing what we observe

    Hmmm... sounds like a great new theory to me...
    cat : Mr. Shrodinger :: experiment : Mr. WaveLength

    Thusly stated: The results of any scientific experiment are not determined until the experiment is actually performed, at which time the "wavefunction" of the experiment-vector collapses; thereafter the results will always be the same, permitting independent confirmation by other scientists.

    Actually I'm somewhat in agreement with you. I have as much faith in the "indeterminism of experiments" as I do in QM. But then I'm just a mathematician, and not a very good one at that.
     
  11. Nov 24, 2003 #10
    Which one is more likely? I would be inclined that due to the difficulty of QCD and the success it has had at prediction (even though it is by far not complete) that it is probably a meson of 4 quarks. That one seems far more likely than needing a whole new QCD. But as was stated, a lot more work is needed to resolve the structure of this meson.


    <edit>vB tags</edit>
     
  12. Nov 24, 2003 #11
    I see that this discussion has basically turned to bashing the results based on the idea that we make our own results when we do experiments by the very fact that we are doing the experiment.

    As a meson spectroscopist, I have to take a moment to stand up for KEK and Fermilab and all the collaborations out there involved in hadron physics. I have reviewed the author's writing, and also the pre-publication of the Belle Collaboration, and I find that X(3872) makes just as much sense as any other particle found so far in the charmonium model. It follows the pattern of charmonium lifetime and decay, and it comes from a decay that is already well tested. If anything, X(3872) is merely a bound state of DD* (a psuedoscalar D-meson and a vector D-meson), which explains its origin (decay from a B+ meson; namely B+ --> K+ + X(3872)), its decay mode (into pi+pi- + J/psi, a vector and two psuedoscalars), its decay width (extremely narrow due to hidden charmness), and its mass (3872 MeV; the D + D* mass combination adds up to 3871.2 MeV, making the DD* composite beautifully exact with some marginal bonding energy to spare). These kind of results don't make themselves up, especially when all you are looking at is a histogram of the decay products after-the-fact, which in this case showed a particular spike at 0.775 GeV in in B-decay invariant-mass plot.

    I am looking forward to reading the full publication when it comes out. I think that this will not lead to a change in the Standard Model, but rather confirm an old theory that mesons with heavy-quark flavors will form bound states that act as mesons themselves, such as the a0(980) and f0(980) scalar mesons are sometimes speculated to be (in their cases, proposed as KKbar bound state candidates).
     
    Last edited: Nov 24, 2003
  13. Nov 24, 2003 #12
    I will agree with mormonator that particle physics is not whatever you make it to be. While the UP does play a role in everything, physics still applies here. Particle interactions will follow very very well defined (even if we have yet to understand them) interaction processes.


    And mormonator, could you direct me to the pre-print on arXiv? Thanks.
     
  14. Nov 24, 2003 #13
    Indeed, the well defined interaction path is probably the most convincing part of the whole thing, in addition to the apparent resonance mass. The whole thing appears to hinge on a bottom quark decaying into a charm-anticharm quark pair and an antistrange quark (perhaps proceeding via flavor-changing neutral current b --> (c + -c) + -s), which is already a known process of the charged weak current via W+ and W-.

    The pre-print is at http://arxiv.org/abs/hep-ex/0309032. You can also check out the link at http://physicsweb.org/article/news/7/11/7 for additional commentary and the link to the pre-print.
     
  15. Nov 24, 2003 #14
  16. Nov 25, 2003 #15
    I looked back on shrodinger and found a better way to say what i need to say (see I can be confusing too).

    If you look at a block of marbel, you can chip a face into it. If you grab a chisil, and are good at this kind of thing. If you have a million blocks, you get a million of the same face. Is this saying that there is a face in the marble? Or is it showing your skill with the proper chisil?

    Its good to see that someone like me, can spark such debate among fine people such as yourselves.

    "But hey, im only 16, what do i know" --Me
    "Math, my dear boy, is nothing more than the lesbian sister of biology" --Peter Griffin
     
  17. Nov 25, 2003 #16
    thankyou

    Thankyou, Ranyart. That is an excellent article I was not aware of previously. By Monday I had guessed that X(3872) is a bound pair of D-mesons, but this really put forward the mechanism for it. I was especially surprised at the magnitude of isospin symmetry breaking that occurs in the DD* model. Also, the unnatural parity precludes X(3872) from being a vector meson, something I had not thought of. Well, I am feeling really good about how I called it before reading this (as you can see, my ego is bulging and about to explode), especially the comparison to a0(980) and f0(980), but this article is very informative and clears up the misconceptions I had. Hopefully I will someday have the time and understanding to interpret all the details properly and fully.
     
    Last edited: Nov 26, 2003
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