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How exactly will LHC detect superpartners?

  1. Sep 16, 2006 #1
    How exactly will LHC detect superpartners? Presumably they will have higher mass, are there other ways to detect them?
  2. jcsd
  3. Sep 16, 2006 #2
    It really depends on the model. In models like the (Minimal Supersymmetric Standard Model) MSSM, there is a quantity called R-parity. Each Standard Model particle has R-parity +1 and each partner has R-parity -1. R-parity is conserved in interactions which means that the lightest partner (R-parity -1 state) will be stable (since it can only has R-parity +1 states that are lighter).

    This Lightest Supersymmetric Partner (LSP) then leaves the detector without being seen. This is a real smoking gun because then the momentum in the plane transverse to the beam will not be conserved by the visible particles (the momentum parallel to the beam isn't either, but this is useless because one doesn't know the initail particle momenta, only their direction).
  4. Sep 16, 2006 #3
    Thanks for the reply.

    I guess while we are on subject, how will LHC see the higgs boson, and how could it see higher dimensions if they exist?
  5. Sep 17, 2006 #4
    I wonder whether such a signature would prove SUSY, as opposed to a non-SUSY previously unknown particle with similiar mass.
  6. Sep 18, 2006 #5
    Yes, to prove it is SUSY you really need to do two things:

    1. Prove the particles differ by spin 1/2.
    2. Prove that the partners have the same couplings as the SM ones.

    I have seen it claimed that 1 is only possible at a linear collider, but there have been some papers more recently on this, e.g. http://arxiv.org/abs/hep-ph/0605067 and http://arxiv.org/abs/hep-ph/0605286, which discuss measurements at the LHC.

    As for the Higgs boson, there are various signals. For example, Higgs decays to two photons are nice because the diphoton invariant mass will give a peak at exactly the Higgs boson mass. This is a rather clean channel, and as soon as it is seen I am sure there will be a discovery announcement.

    However, again, one has to be careful to make sure it is a Higgs and not something else. To do this, you really need to measure its spin (to see it is a scalar) and its couplings (to show they are proportional to the mass of the particle it couples to). Eventually if you can measure its self couplings you can actually reconstruct the shape of the mexican hat potential of the Higgs boson. Unfortunately this last thing won't be possible at the LHC.
    Last edited by a moderator: Apr 22, 2017
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