Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

SM Higgs ruled out over wide range (26 July announcement)

  1. Jul 26, 2010 #1


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    "The bottom line is that CDF and D0 can now exclude (at 95% confidence level) the existence of a Standard Model Higgs particle over a fairly wide mass range in the higher mass part of the expected region: from 158 to 175 GeV. If the SM Higgs exists, it appears highly likely that it is in the region between 114 GeV (the LEP limit) and 158 GeV."
    http://www.math.columbia.edu/~woit/wordpress/?p=3073 New Higgs Results from the Tevatron

    Press release from Fermilab:
    Last edited: Jul 26, 2010
  2. jcsd
  3. Jul 26, 2010 #2
    The bottom line is that Tevatron wants a 3 year extension.

    In particular, I personally do not buy their answer to :
    Predictions for Higgs production at the Tevatron and the associated uncertainties
    They answer here essentially by
    My experience with PYTHIA is that the underlying models are insufficient to reproduce multidimensional correlations in non-perturbative hadronic phenomena, including (especially in this context, high) transverse momentum dependence. They have uncontrolled systematic errors stemming from the uncertainty in the energy scale, which have not properly been taken into account in uncertainties associated with partons distributions.

    In addition, the final sensitivity they get is rather weak. Using blindly a big black box to make a weak claims based on uncontrolled systematic errors may suffice to convince budget people for a 3 years extension run, but I have no doubt that it will not convince theoreticians on the other side of the ocean.
    Last edited: Jul 26, 2010
  4. Jul 26, 2010 #3


    User Avatar
    Gold Member

    "The bottom line is that Tevatron wants a 3 year extension."

    I hope they get their three year extension. At the end of that time, hopefully CERN and FermiLab see the same signal or lack thereof.
    Jim Graber
  5. Jul 26, 2010 #4
    If I believed they had addressed their systematic errors, I would heartily agree. Unfortunately, there was lately not a single month without Tevatron claiming a 1 or 2 sigma BSM signal.

    A 3 years extension for Tevatron is a lot of money for something that will be done better in 2 months of LHC. Besides, I surely hope the ILC will cross-check (and go beyond) the LHC.
  6. Jul 26, 2010 #5


    User Avatar
    Gold Member

    Oh Hi humanino,
    How soon do you think we will get the ILC?
    I fear it is a very long time.
    Jim Graber
  7. Jul 26, 2010 #6
    That is true, if it starts before I retire, I'll be lucky. I think reasonably it could start around 2040 +/- 10 years.
  8. Jul 26, 2010 #7


    User Avatar
    Gold Member

    Hi, humanino,
    About the ILC you may be even more pessimistic than I am.
    But I am already past normal retirement age and don't expect to see ILC results in my lifetime.

    Returning to the subject of not seeing Higgs bosons.
    I think I understand you to be skeptical of the Tevatron exclusion result due to doubts about the theoretical prediction part,
    rather than the observation part. But in either case, what is needed is more data, I think.

    I have some more questions about how much data is needed:
    I dug up the quote below from one of your posts in another recent thread:

    Start Quote
    One can readily list the 4 logical possibilities and conclude from them :
    there is one Higgs boson, the standard model is essentially correct, everything is quite boring and the LHC just confirms the model measuring the Higgs boson mass. Quite unlikely, but "there is something" (the old single Higgs boson)
    there is at least one Higgs boson, but the standard model is not the full story. Very interesting and likely possibility, "there is something" (at least one Higgs boson)
    there is no Higgs boson, but since the standard model without Higgs boson predicts that quantum unitarity is violated in vector boson scattering amplitudes at about half a TeV, something else comes in to save probability conservation at the end of the day. No Higgs boson but still a Higgs mechanism. In any case again, "there is something" (possibly technicolor or the likes)
    there is no Higgs boson and no Higgs mechanism, the Higgsless standard model is the end of the story. It appears you conclude : "there is nothing". But you forgot that within this logical possibility we can predict that quantum unitarity is violated : nobody believes this will happen, yet that would be a scientific revolution. Either probabilities are not conserved (do not sum up to 1), or quantum mechanics is wrong. So in fact it is quite clear that this logical possibility entails that "there is something"
    End Quote

    I would like to ask about what happens if possibilities one and two, or one, two and three are not realized.
    How much data will it take before people conclude that the Higgs is not there, and go on to the more radical possibilities?
    Also, if we only see one Higgs, when will it be regarded as a standard Higgs, rather than merely the first supersymmetric Higgs?
    Jim Graber
  9. Jul 28, 2010 #8
    Last edited: Jul 28, 2010
  10. Jul 31, 2010 #9


    User Avatar
    Gold Member

    Now that the slides are up, this is a very good reference for recent details.
    Thank you humanino for such a good reference.

    Slide 35 of this talk seems to answer my question in my previous post:

    If a more or less standard or supersymmetric Higgs exists, it is expected to be found with only ten or twenty inverse femtobarns of data,
    but something more exotic such as technicolor or a higgsless model will require more than one hundred inverse femtobarns.
    I think the former is exected in two or three years,or four at the most, but the latter may be five to seven years out.
    I have searched future luminosity schedules, but that seems to be another rather complicated subject.
    Jim Graber
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook