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

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Discussion Overview

The discussion centers around the recent announcement regarding the exclusion of the Standard Model Higgs particle over a significant mass range, as reported by CDF and D0. Participants explore implications for future experiments, particularly the Tevatron and the ILC, and express skepticism about the reliability of current predictions and results related to Higgs production.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants note that the CDF and D0 results exclude the existence of a Standard Model Higgs particle in the mass range from 158 to 175 GeV, suggesting it is likely between 114 GeV and 158 GeV if it exists.
  • Concerns are raised about the reliability of predictions for Higgs production at the Tevatron, particularly regarding the use of PYTHIA simulations and associated uncertainties.
  • Some participants express skepticism about the Tevatron's claims of observing signals, citing a history of inconsistent results.
  • There is a discussion about the potential need for more data to conclude definitively about the existence of the Higgs boson and the implications of not finding it.
  • Participants speculate on the timeline for the International Linear Collider (ILC) and express doubts about its realization within their lifetimes.
  • One participant references logical possibilities regarding the Higgs boson and questions how much data would be necessary to rule out certain scenarios.
  • There is a mention of a forthcoming discussion in Paris that may address some of the concerns raised about the Higgs production predictions.
  • Another participant shares insights from a recent talk, indicating that finding a standard or supersymmetric Higgs may require significantly less data than more exotic models.

Areas of Agreement / Disagreement

Participants express a range of views, with some agreeing on the need for more data and skepticism about current results, while others emphasize different aspects of the predictions and implications. Overall, the discussion remains unresolved with multiple competing perspectives on the reliability of the Tevatron's findings and the future of Higgs research.

Contextual Notes

Participants highlight limitations related to the theoretical predictions and uncertainties in the models used for Higgs production, as well as the complexity of future luminosity schedules for experiments.

Who May Find This Useful

This discussion may be of interest to researchers and students in particle physics, particularly those focused on Higgs boson research, experimental methodologies, and the implications of current findings for future experiments.

marcus
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"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:
http://www.fnal.gov/pub/presspass/press_releases/Higgs-mass-constraints-20100726.html
 
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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
We disagree [... based on our simulations with] PYTHIA

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.
 
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"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.
Best.
Jim Graber
 
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.
 
Oh Hi humanino,
How soon do you think we will get the ILC?
I fear it is a very long time.

Jim Graber
 
jimgraber said:
How soon do you think we will get the ILC?
That is true, if it starts before I retire, I'll be lucky. I think reasonably it could start around 2040 +/- 10 years.
 
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 into 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?
TIA
Best.
Jim Graber
 
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humanino said:
The authors of this paper will provide further discussion in a talk tomorrow in a special meeting being organized in Paris. I understand that they already agree with my above claims, and expect tomorrow's discussions to be lively.

Now that the slides are up, this is a very good reference for recent details.
http://indico.lal.in2p3.fr/conferenceDisplay.py?confId=1109
Thank you humanino for such a good reference.

Slide 35 of this talk seems to answer my question in my previous post:
http://indico.lal.in2p3.fr/getFile....ionId=7&resId=0&materialId=slides&confId=1109

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
 

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