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22 July rumor: Higgs at 144 GeV and anti-Higgs at 350 GeV (comment?)

  1. Jul 22, 2011 #1

    marcus

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    http://www.math.columbia.edu/~woit/wordpress/?p=3851&cpage=1#comment-95199
    "News from EPS: a higgs at 144 GeV and a anti-Higgs at 350 GeV"


    Blogging from the EPS meeting at Grenoble. As of 22 July:
    ATLAS and CMS Summarize Their Higgs Searches
    http://profmattstrassler.com/2011/07/22/atlas-and-cms-summarize-their-higgs-searches/ [Broken]
     
    Last edited by a moderator: May 5, 2017
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  3. Jul 22, 2011 #2

    bcrowell

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    I wouldn't call it a rumor. It seems to be straight from the horse's mouth. However, what we're hearing from the horse's mouth is that basically they do not have statistically significant evidence for the Higgs:

    If they had 2.8 sigma after the look-elsewhere effect, it would be worth following up on, but not be particularly exciting. The fact that they have 2.8 sigma before the look-elsewhere says that it means absolutely nothing at all.
     
  4. Jul 22, 2011 #3

    Vanadium 50

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    Absolutely nothing? No, it means 8%. :smile:

    There are people here who immediately went to work trying to combine everything "by eye". That seems to me to be a real waste of time - it won't convince anyone, and it's impossible to do properly, at least for an outsider. These limits are not completely independent - background cross-sections, for example, are common to both.

    What is certainly true now is that the LHC experiments are sensitive to a large region of possible Higgs masses. That was not true a few months ago.
     
  5. Jul 22, 2011 #4
    Why is the Higgs so hard to find.
    I'm very excited about the research going on at the LHC as I have said before I believe that the LHC is going to give us more answers than we have questions for right now.
    The technology is very advanced and powerful and should provide a wealth of information that will keep scientist busy for years to come.
    But back to my question why is the Higgs-Boson so hard to find?
    Isnt the Higgs suppose to exist in large quantities?
     
  6. Jul 22, 2011 #5
    Do the models or the properties of the Higgs predict that it will be so hard to find?
     
  7. Jul 22, 2011 #6

    tom.stoer

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    b/c the experiments which are designed to produce the Higgs do not ONLY produce the Higgs but zillions of other particles as well; so it's like to find a a pin in a haystack; given the haystack you have to be absolutely sure that you know in detail the quantity of the hay; thenyou subtract the hay from the measurement and what you get is the pin
     
  8. Jul 22, 2011 #7
    So then could we have already exposed the Higgs and we just havent been able to pick it out of a line up yet, so to speak?
     
  9. Jul 22, 2011 #8

    tom.stoer

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    yes, that's possible
     
  10. Jul 22, 2011 #9

    marcus

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    Nature News reported on this today:
    http://www.nature.com/news/2011/110722/full/news.2011.435.html
    ==sample excerpt==
    Collider sees tantalizing hint of Higgs
    Excess events suggest LHC is homing in on elusive particle.

    Geoff Brumfiel

    For now, physicists are only willing to call them 'excess events', but fresh data from two experiments at the Large Hadron Collider (LHC) are hinting at something unusual — and it could be the most sought-after particle in all of physics.

    Both ATLAS and the Compact Muon Solenoid (CMS) experiments are seeing an unusual surplus of events in a rough mass range of 130–150 gigaelectronvolts (energy and mass are used interchangeably in particle physics). The data are far from conclusive, but physicists believe this could be the first indication of the Higgs particle, believed to be responsible for the masses of other particles. The results were presented this afternoon at the Europhysics Conference on High Energy Physics in Grenoble, France.

    Physicists familiar with the experiments urge caution. The new data are a long way from a discovery, says Matthew Strassler, a theoretical physicist at Rutgers University in New Jersey. "I would call it tantalizing."...
    ==endquote==

    Nature magazine is like Science magazine quality-wise. Its journalism is better than most. More reliable than "Science Daily" or "New Scientist". So I tend to think they give a fair picture, to the extent one can at this stage. Better not get your hopes up. But it is interesting to know about nevertheless.
     
    Last edited: Jul 22, 2011
  11. Jul 22, 2011 #10

    bcrowell

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    The Nature article is even worse. Doesn't give any quantitative discussion of the statistics.
     
  12. Jul 23, 2011 #11

    Vanadium 50

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    The discussion doesn't exist. ATLAS says the probability a Higgsless dataset will fluctuate to look like what they see is 8%. That's it. CMS did not provide a similar number, and as I said above, you can't just naively combine these results and get anything except nonsense. The experiments are working on a combination; if they are very lucky, we will see it in a month.
     
  13. Jul 23, 2011 #12

    bcrowell

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    This seems to be a response to my posts, but it doesn't seem to relate to what I said. I didn't say anything about combining the results.
     
  14. Jul 23, 2011 #13

    Vanadium 50

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    My point is that we have only one number - ATLAS 8% - and any serious statement about what the LHC sees needs the other number, plus the combination.
     
  15. Jul 24, 2011 #14
    Could you explain what the 8% represents?
     
  16. Jul 24, 2011 #15

    naima

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    look at the curve in http://en.wikipedia.org/wiki/Standard_deviation" [Broken]
     
    Last edited by a moderator: May 5, 2017
  17. Jul 24, 2011 #16

    bcrowell

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    It's the probability that ATLAS would have seen a peak this strong, sticking up above the background somewhere, when in fact background was all there was.

    For comparison, the gold standard for claiming discovery of a particle by direct detection is usually taken to be 5 sigma, which is a probability of about 10^-7.
     
  18. Jul 24, 2011 #17
    So there an 8% chance that there is not a Higgs particle, based on these results?
     
  19. Jul 24, 2011 #18

    bcrowell

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    Not really. There's an 8% chance that they would get these results if there is no Higgs.

    For comparison, suppose that someone tells me he's done an experiment to look for ghosts in a haunted house, the results were positive, and the probability is 0.1% that he would get these positive results if ghosts aren't real. Should I now say that there is a 0.1% chance that ghosts don't exist, and a 99.9% chance that they do? No, because the existence of ghosts is something to which I assign a very small a priori probability.

    Suppose that I had access to secret data showing that the Higgs definitely existed, and had the energy where they see this peak. Then the a priori probability would be 100%, and I would assign a 100% probability to the statement that what they saw was the Higgs.

    The thing is, there is no neutral a priori probability here. E.g., it doesn't make sense just to say the the a priori odds of existence of the Higgs in this energy range are 50/50.
     
    Last edited: Jul 24, 2011
  20. Jul 24, 2011 #19

    Berlin

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    Is there a natural extension of the SM predicting a different mass for the anti-higgs to the higgs? Maybe also quantatively?!

    berlin
     
  21. Jul 24, 2011 #20

    bcrowell

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    This seemed very mysterious to me in the anonymous post on the Woit blog. It doesn't seem to be mentioned in the Strassler page or the Nature article. Isn't the Higgs supposed to be its own antiparticle? And I've never heard of an antiparticle having a different mass from the particle itself. In any case, it seems premature to talk about changing the standard model when there is actually no firm evidence that the Higgs has even been detected.
     
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