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Supersymmetric Particles

  1. Aug 19, 2005 #1
    What are the relationships between particles and their superpartners, other than that the supersymmetric particles have 1/2 less spin than the 'normal' particles? For example, do the pairs of particles have the same force charges?
     
  2. jcsd
  3. Aug 20, 2005 #2

    arivero

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    Yes, there are grouped into Supermultiplets, so that the particles in a same multiplet differ only in spin, very much as the two components of an spin doublet differ only in the Z proyection +1/2, -1/2.
     
  4. Aug 20, 2005 #3

    EL

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    If supersymmetry was unbroken the masses would also be equal. However, since we do not observe any superpartners at such low energies, supersymmetry must be broken.
     
  5. Aug 20, 2005 #4

    arivero

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    My preonic oppinion, is that the muon is SUSY to the pion so it is not so badly broken.
     
  6. Aug 21, 2005 #5

    EL

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    But the pion is composed out of a quark/antiquark. Could that really work anyway?
     
  7. Aug 21, 2005 #6
    No, it doesn't work since the pions are strongly interacting and the muon isn't.
     
  8. Aug 21, 2005 #7

    arivero

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    Hmm the pion is not exactly strongly interacting; it is the carrier of the strong nuclear interaction. To say that it is strongly interacting is as to say that the photon is electromagnetically interacting.

    As for SU(3) charge, the pion is neutral, as the muon is.

    Furthermore, the same trick works with quarks, they can be put as SUSY to diquarks. This task was taken by a student of Georgi, but he did not pursue it.
     
  9. Aug 21, 2005 #8
    The degrees of freedom don't match here. Are you including a scalar isosinglet with the pions?

    Also, where are the partners of the electron and the tau?
     
  10. Aug 22, 2005 #9

    arivero

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    An scalar isosinglet with the pions? You mean, eta? Or do you mean that pions and eta are pseudoscalars, not scalars. The point then is the eigenstate of parity, and I am not sure of how this works in susy theories (they use Weyl spinors, do they?).

    No problem for tau, its mass is near the charmed mesons, and even no so far from the B ones (after all, Susy is broken, even if not as badly as in usual models)

    As for the electron, it all depends of the situation when susy is restored. It is probably massless. So it doesnt need partner after all. If we would like it to have a partner, then we should hope the pion to be massless in the limit when susy is restored, and hope that the kaon mass becomes partner with the muon. It seems to me a solution uglier that having pions and muons partnered.


    Of course all the game of SUSY has sense if it serves to control the divergences in the Higgs field. So while a "biquark susy" pairing could explain why the masses of muon and tau are so coincident with the meson spectra, the real question is what kind of higgs sector would appear in this susy scheme.
     
  11. Aug 22, 2005 #10

    Mk

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    What does preonic mean?
     
  12. Aug 23, 2005 #11

    arivero

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    See the thread https://www.physicsforums.com/showthread.php?t=76937
    Preon is generic name for the components of a quark or a lepton. This covers a lot of different models, usually they are grouped in this way in order to establish generic non-go theorems.

    It is true that here "preon" is a bit forced, because only the susy partner has components, and they happen to be the original set of fermions. Perhaps including three families (so tau could be partner of a bottom fermion instead of a charmed one, or charm could be parted to an antibottom plus an antidown, etc).
     
  13. Aug 23, 2005 #12
    Supersymmetry relates degrees of freedom. The muon has four, and the pions only 3 (now that I think about it, the neutral pion can't be SUSY to a charged particle anyway, so really 2). That's 4 fermionic degrees of freedom for 2 scalar d.o.f, so it seems like you would need to find 2 more scalars to include in the supermultiplet for this to have a chance of working.
     
  14. Aug 24, 2005 #13
    If it is true (as suggested by Selectron in the first post) that supersymmetry particles always have 1/2 spin less than "normal particles", then one hypothesis to explain this aspect of supersymmetry is that we have a unique relationship between deuteron nucleon clusters [NP], which are bosons with spin = 1, and 3-nucleon clusters {e.g., helium-3 [PNP], triton [NPN]}, which are fermions with spin = 1/2. The equation that predicts a supersymmetry type relationship between these boson and fermion clusters is 3[NP] = 1[PNP] + 1 [NPN]. Thus we see that the mirror fermion particles have 1/2 spin less than boson [NP]--but it is not clear to me that the term "normal" for bosons is correct--e.g., bosons are no more normal than fermion nucleon clusters if they are supersymmetry mirror entities.
     
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