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Given that the gluino is in the same representation of SU(3) that the gluon and so the same kind of interaction vertexes with quarks, I guess that it could have a role in the strong force. But there are obvious differences: being a fermion, there is no a classical field, and as you can not accumulate fermions in the same state surely its role in the formation of a QCD string field at long distances is minor, but it is still possible to have pairs of gluino/antigluino bubbling out from the vacuum.

So, how is it? How different is the strong force in a meson with QCD from a meson of sQCD? Can sQCD have mesons of spin 1/2? Has sQCD still a coloured string between quark and antiquark, and if so, has it still the same tension that the QCD string? Is there some remarkable difference between QCD meson and baryons and sQCD composites?

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The gluino does indeed change QCD, however as you probably can guess its a very small modification. A gluino pair is able to pop in and out of the vacuum and will also change the interaction between two quarks. However, due to its necessarily large mass it won't be a large effect. Also since it is a fermion it can't interact directly will quarks (it must go through a gluon). Thus I would expect its effect on quarks to be further suppressed.

In a similar way the Z boson slightly modifies the energy levels in atoms (though can in fact be observed for heavy atoms), but these effects can safely be ignored 99.9% of the time.

You asked about the SUSY QCD bound state spectrum. Due to the gluino it is indeed modified. You can now have the additional gluino states, $\tilde{g}g,\tilde{g}\tilde{g},\tilde{g}q \bar{q},...$.

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  • $\begingroup$ Really a spin 1/2 $\bar g q \bar q$ is valid? or do you mean $\bar g \bar g q \bar q$ $\endgroup$
    – arivero
    Sep 13 '14 at 12:17
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    $\begingroup$ No, I meant $\tilde{g}q \bar{q}$. This can be seen using the technique of combining representations of fields known as Young Tableux. I suspect its beyond the scope of the question but in group language a quark and an antiquark make $\bar{3} \otimes 3 = 8 \oplus 1$ and the $8$ can then combine with the $8$ of a gluino to form a singlet. You can however also have $\tilde{g}\tilde{g} \bar{q} q$ (which again can be shown using Young Tableux). $\endgroup$
    – JeffDror
    Sep 13 '14 at 12:22
  • $\begingroup$ It is well in the scope :-) $\endgroup$
    – arivero
    Sep 13 '14 at 16:46

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