Discovery of Higgs: Does this mean anything to String theory?

  • #1

Main Question or Discussion Point

Hi PF

Does the discovery of the Higgs Boson mean anything to string theory ? Does it falscify or verify the theory, or is it completely irrelavant for the theory?

\Schreiber
 

Answers and Replies

  • #2
bcrowell
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The Higgs hasn't been discovered. Don't overinterpret a leaked, preliminary version of a tentative result.
 
  • #3
Im not talking about the rumors (yes I have seen them). I just wondered, if we discover the Higgs Boson, what would it mean to string theory's existance :)
 
  • #4
I am not 100% sure, but I thought the mathematics of String Theory inherently predicts the existence of the Higgs, therefor if it is found, becomes sort of a partial-proof of String theory's validity.
 
  • #5
It's not something unique to String Theory, so while it does predict a Higg's-like particle, it would be no coup.
 
  • #8
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That would be very exciting; would a high energy Higgs be a blow to SUSY?
yes, pretty much, but people will tell you it is still possible, I'm not an expert on the calculations but I feel that even many of the experts will give up on SUSY if higgs isn't < 120gev
 
  • #9
fzero
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That would be very exciting; would a high energy Higgs be a blow to SUSY?
The low-mass Higgs is a feature of minimal supersymmetric models, i.e. one adds the minimum amount of new particles to the Standard Model to obtain a model that is supersymmetric above the electroweak scale. Having the scale of SUSY and electroweak symmetry breaking related would provide a solution to the so-called hierarchy problem: how to understand why quantum corrections to the Higgs mass are so small. This is a big motivation for supersymmetry, so if these scales are not related, SUSY becomes less interesting. There is a bit of room to play with depending on what else is seen at the LHC. The mass of the lightest Higgs could be larger in supersymmetric models that also include new physics such as additional generations or new gauge interactions. So it's very important to have as much data as possible to either observe or exclude as much potential new physics as possible before drawing conclusions.

There are other motivations, such as coupling constant unification, that don't depend on the scale of electroweak symmetry breaking. So it could be the case that SUSY is relevant to grand unification, but not to lower energy physics. Unfortunately, such a scenario probably only offers indirect tests.
 
  • #10
Thanks unusualname and fzero for your answers, I've learned some things today.
 
  • #11
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yes, pretty much, but people will tell you it is still possible, I'm not an expert on the calculations but I feel that even many of the experts will give up on SUSY if higgs isn't < 120gev
What does giving up on SUSY mean for String Theory?
 
  • #12
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What does giving up on SUSY mean for String Theory?
It means all the results from string theory consistent with supersymmetry would not be so significant.

It would not mean string theory is wrong, just that its consistency with the susy model was a red herring.
 
  • #13
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It means all the results from string theory consistent with supersymmetry would not be so significant.

It would not mean string theory is wrong, just that its consistency with the susy model was a red herring.
I'm an amateur, at best, when it comes to String Theory. I've only studied as far as analyzing open and closed strings under bosonic String Theory (26D)

I thought to be able to account for fermions and bosons you needed superstrings, which utilized SUSY, hence the name? Is that correct?

I was under the impression bosonic String Theories are generally regarded as unphsyical (not too mention they only account for forces, and not matter)

If so, it seems like if you take away SUSY and therefore superstrings, there wouldn't be much left of the theory.
 
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  • #14
PAllen
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It means all the results from string theory consistent with supersymmetry would not be so significant.

It would not mean string theory is wrong, just that its consistency with the susy model was a red herring.
I will state up front that I cannot comment on this at all, from my own knowledge. However, whatever people may say about his (e-)personality, I think most would agree Lubos Motl can say a little about string theory:

http://motls.blogspot.com/2010/06/why-string-theory-implies-supersymmetry.html

This suggests that absence of supersymmetry would be a major problem for string theory. However, even the LHC at full energy and luminisity cannot completely dis-prove supersymmetry.
 
  • #15
bcrowell
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This suggests that absence of supersymmetry would be a major problem for string theory. However, even the LHC at full energy and luminisity cannot completely dis-prove supersymmetry.
Can any experiment ever falsify supersymmetry, or can one just say that the symmetry is more and more approximate as data become available at higher and higher energies?
 
  • #16
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Can any experiment ever falsify supersymmetry, or can one just say that the symmetry is more and more approximate as data become available at higher and higher energies?
I don't think there is any upper bound on where susy breaks. But the higher you go the less useful susy becomes for explaining various phenomenological data (eg if it's not at or around LHC level it means that it's not susy solving the hierarchy problem). And of course the less helpful susy is the less people will expect it to exist. If it solves lots of problems it's likely to be there, if it doesn't solve any problem there's no reason to expect it.

But that's of course just for phenomenological issues. Susy will continue to be useful and used even if we don't find it by the planck scale. Cause I don't know about you guys, but when I do my QCD gluon scattering amplitudes I still use susy

Also regarding string theory. If you do a non -susy string theory, usually the tachyon condensation takes you to a susy theory. There's nothing wrong or bad with the tachyon, that's just an old way of thinking about it. Tachyon just means you're doing perturbation theory where you shouldn't. But if you can solve the condensation issue you're perfectly fine - you'll just end up in a different theory. However there are some possible string models which won't always force you into susy. I know Klebanov is working on them and is making some progress
 
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  • #17
PAllen
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Can any experiment ever falsify supersymmetry, or can one just say that the symmetry is more and more approximate as data become available at higher and higher energies?
I guess if SUSY breaking is at Planck scale, no. I suspect, in practice, most interest will be lost if not found with full energy at LHC. Lubos Motl admits he'll be dumbfounded and consider it a big problem if no SUSY particles are found below 10 TEV. Unfortunately, LHC at full energy cannot be expected (with much likelihood) to produce 10 TEV SUSY particles. So Lubos has defined himself as safe for a very long time.
 

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