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I Is the new 3.0 TeV bump at ATLAS a fluke?

  1. Jul 24, 2017 #1

    ohwilleke

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    The ATLAS experiment has seen a bump that could be a new particle at a mass of 3.0 TeV/c^2 with a local significance of more than three sigma, and a global significance of a bit more than two sigma in Run-2 data looking at decays of qqbb states to a W or Z boson and a Higgs boson.

    It is possible to fit this into a "heavy vector boson" hypothesis (such as a W' or Z' model), but I think it is more likely to be a fluke, as it isn't very well motivated and has a low global significance. The preprint is as follows:

    arXiv:1707.06958 [pdf, other]
    Search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq¯(′)bb¯ final state in pp collisions at s√=13 TeV with the ATLAS detector
    ATLAS Collaboration
    Comments: Comments: 18 pages plus author list + cover pages (36 pages total), 5 figures, 4 tables, submitted to PLB, All figures including auxiliary figures are available at this https URL
    Subjects: High Energy Physics - Experiment (hep-ex)

    A search for heavy resonances decaying to a W or Z boson and a Higgs boson in the qq¯(′)bb¯ final state is described. The search uses 36.1 fb−1 of proton-proton collision data at s√= 13 TeV collected by the ATLAS detector at the CERN Large Hadron Collider in 2015 and 2016. The data are in agreement with the Standard Model expectations, with the largest excess found at a resonance mass of 3.0 TeV with a local (global) significance of 3.3 (2.1) σ. The results are presented in terms of constraints on a simplified model with a heavy vector triplet. Upper limits are set on the production cross-section times branching ratio for resonances decaying to a W (Z) boson and a Higgs boson, itself decaying to bb¯, in the mass range between 1.1 and 3.8 TeV; the limits range between 83 and 1.6 fb (77 and 1.1 fb) at 95% confidence level.
     
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  3. Jul 24, 2017 #2

    Orodruin

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    These are the key words. This is not even a 3 sigma deviation from the SM.
     
  4. Jul 24, 2017 #3

    ohwilleke

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    I don't disagree, but I pretty much guarantee that it will produce a bunch of phenomenology papers at arXiv as it is one of the bigger bumps or anomalies out there that hasn't been around for years.
     
  5. Jul 24, 2017 #4

    Orodruin

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    Oh, I don't doubt that it will. There is a high chance those will be thrown in the trash bin in one year's time.

    I do not think it is bad per se to explore the possibility of a signal. It becomes bad when you jump at every 2 sigma deviation while yelling "This is it!" since, most likely, it isn't.
     
  6. Jul 26, 2017 #5

    Demystifier

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    Bad for who? If you are wrong, everybody will forget it soon anyway. If you are right (the chances are small, but still), you will become a hero. :biggrin:
     
  7. Jul 26, 2017 #6

    Orodruin

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    I disagree. I know of several people who are well known for being people who cry wolf ...
     
  8. Jul 26, 2017 #7

    Demystifier

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    OK, can you give their names?
     
  9. Jul 26, 2017 #8

    Orodruin

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    Resorting to what amounts to slander on an open forum on the internet where they have no opportunity of responding and if they do where I am easily identifiable? I don't think so.
     
  10. Aug 1, 2017 #9

    mfb

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    Or faster if CMS won't have a bump at the same place.

    The small excess ATLAS has is higher than the expectations for the model they test. If that would be a signal, it would be an unexpectedly strong one.
     
  11. Aug 1, 2017 #10

    Orodruin

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    Let me reformulate to my intended meaning: "will have been thrown away one year from now" :rolleyes:
     
  12. Aug 26, 2017 #11

    ChrisVer

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    I didnt have the time to read through the whole analysis in the paper, yet I find it interesting...
    I wonder why they don't mention signal systematics (like PDF systs)....
     
  13. Aug 27, 2017 #12

    mfb

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    The background estimate is from data, no PDFs involved. The potential signal strength is just given in terms of cross section, again no PDFs involved. There are some uncertainties related to MC, they are discussed on page 10.
     
  14. Aug 27, 2017 #13

    ChrisVer

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    No, I was asking for signal systematics, not SM bkg...
     
  15. Aug 27, 2017 #14

    mfb

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    The background description is part of the systematic uncertainty of the signal yield. It is often the largest contribution, because "(observed-background)/efficiency" is the signal (simplified description), and the number of observed events is known and the efficiency is often well-known as well.
     
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