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

Why no supersymmetric partners?

  1. Jan 3, 2006 #1
    Quoting from Lisa Randall’s book, Warped Passages, page 343:

    “We have seen that supersymmetry can elegantly protect the hierarchy and guarantee that all the large quantum mechanical contributions to the Higgs particle add up to zero. But, as we saw in Chapter 13, even if supersymmetry exists in nature, it must be broken to explain why we’ve observed particles but not their superpartners”

    She goes on to indicate that broken symmetry cannot be correct and suggests that the hierarchy problem (i.e., the 16 orders between the Planck mass scale and the weak force mass scale) could be solved by removing the supersymmetry breaking to a separate brane.

    However, there may be another explanation for the lack of detectable superpartners. It seems well established that during the Big Bang when the particles recombined with or annihilated anti-particles, that only a tiny fraction of the original number of particles were left over due to CP violation to become all that we can see in the physical universe. Now perhaps if the number of superpartner particles were exactly equal to the number of superpartner anti-particles, then there would be no leftover superpartners in nature. Then broken supersymmetry would not be required to explain the lack of superpartner detections, and virtual superpartners could have exactly the same properties in mass and charge as virtual particles; thus making the supersymmetric solution of the hierarchy problem almost exact.

    Wikipedia suggests that CP violation of the weak force alone accounts for only a tiny fraction of the mass of the universe. So I gather that this is an unsolved problem for matter, and presumably also for the superpartners. Thus complete annihilation of the superpartners is a possibility. Can some of you comment on that possibility? In particular is it a well known possibility or easily forbidden?

    Richard Ruquist
  2. jcsd
  3. Jan 3, 2006 #2


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Another possibility is that there is no supersymmetry, except the BRST "ghost" supersymmetry that is inherent in gauge field theory.
  4. Jan 3, 2006 #3
    Would the BRST "ghost" supersymmetry solve the heirarchy problem?
  5. Jan 3, 2006 #4


    User Avatar
    Gold Member

    Good point, yanniru.
  6. Jan 3, 2006 #5


    User Avatar
    Gold Member

    A thing I was thinking recently is if we can control the hierarchy by using diquarks and pseudoscalars, which -thanks to having three generation- happen to occur in the exact number of degrees of freerom that the elementary fermions.
  7. Jan 4, 2006 #6
    Supersymmetric virtual particles

    Here is an argument against the existence of exact supersymmetry, where exact supersymmetry means that the superpartners have the exact properties of the partner partners except for spin and CP violation.

    The heirarchy problem is solved with supersymmetry by essentially eliminating the effectiveness of virtual particles. For example, the strong force confinement of quarks depends on the accumulation of virtual particles as the quarks separate- at least that is what I read. But with exact supersymmetric cancellation of the virtual particle effect, that seemingly could no longer be true.

    I am also wondering if the supersymmetric cancellation of anomolies in superstring theory is related to this problem. Seems at least in the virtual particle case that the effect is mediated rather than cancelled. But in superstring case it should be cancellation rather than mediation.
  8. Jan 4, 2006 #7


    User Avatar
    Gold Member

    Hmm, if it were possible to elaborat it (I doubt), the argument aims against supersymmetry in the gauge sector, but it still remains susy in the matter sector. In fact, it is susy with the elementary fermions which is needed to control the hierarchy divergence in the Higgs mass.

    Note the peculiar point that the coupling constants between Higgs field and other particles are proportional to the mass. This does not happen with usual gauge couplings.
    Last edited: Jan 4, 2006
  9. Jan 4, 2006 #8
    Consider the vacuum energy

    Well, I have to profess ignorance of the matter and guage sector. So allow me to pose a different question: If susy solves the Higgs heirarchy problem by cancelling or at least mediating the effectiveness of virtual particles, would it not also reduce the vacuum energy as well?
  10. Jan 4, 2006 #9


    User Avatar
    Gold Member

    I call matter to the standard model fermions, and force to the gauge bosons. Just nomenclature.

    As for the vacuum, yep, a property of any unbroken SUSY is that the lowest energy state has eigenvalue zero. So I would suspect that vacuum energy disappears from the view. But perhaps all the vacuum energy theme is a wrong take, according a recent paper of Jaffe.
  11. Jan 4, 2006 #10
    vacuum energy

    Thanks, arivero. That clears alot up for me. But then why do so many worry that the vacuum energy is 120 orders of magnitude too small? Seems rather that the small vacuum energy is evidence for susy.
  12. Jan 4, 2006 #11


    User Avatar
    Gold Member

    I can not be of more help here, but I hope some other taker can. Any?
  13. Jan 5, 2006 #12
    I do believe that there is a Randall+Sundrum? paper that I have to check, from sometime ago that made handwavings to the 'choice' of Universe 'era', specifically an expanding or contracting era?

    The question can be similar to here:https://www.physicsforums.com/showthread.php?t=104934

    with the 'era' being pahse dependant, for instance for evolving from an expanding phase, the symmetry is broken via particle production at an epoch close to the Big-Bang. All the resulting particles are configured and evolve into matter, redistributed by Stars, Galaxies.etc..

    Now for the 'super-symmetry' particle counterparts, they are behind the event-horizon of Black-Holes (there are some models that maintain that Blackholes are infact super-particles themselves:Hawking-Blackholes aint so Black.), but, for the Universe that is "actually" in contraction, the super-symmetry (missing) particles appear close to the Big-Bang, as the density of matter is configured and squeezed.

    I will try and dig out the actual paper, but I know the speculation was followed by a number of other theorists.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook