Please help me with two very silly questions.

Assuming supersymmetry is correct, why don't we observe the superpartners of the Standard Model particles at ordinary energies? Why do we have to search for selectron in colliders when we could easily observe electrons at ordinary energies? Is selectron much heavier than an electron to exist at ordinary energies?

If supersymmetry gets excluded at LHC, what would it mean for Superstring theory which I guess requires supersymmetry to be true?

  • $\begingroup$ Hi, I was just looking at my previous answers and wonder if you have any further questions (or objections!) to the one here. If not, then would you consider accepting it? $\endgroup$ – Helen - down with PCorrectness Jan 7 at 15:32
  • $\begingroup$ Thanks to the OP! $\endgroup$ – Helen - down with PCorrectness Jan 8 at 15:44

Three points to be answered here:

  • Precisely because we don't see any superpartners at "standard model" energies, it follows that if supersymmetry exists then it must be a broken symmetry. All current experimental searches check theoretical models of broken susy. There are various ways for this breaking to proceed theoretically.

  • Superstring theory is based on the assumption of susy, therefore it won't be valid if susy is wrong.

  • An important point, and one of the main reason why many physicists dislike susy: it cannot "get excluded at LHC" (or any other future stronger collider). The models describing susy have already been twisted to the extreme, giving rise to a practically infinite range of parameter values, and this is still proliferating. By construction, susy can't get excluded.

So experimentalists have to decide which sets of parameter values to focus on; the most popular ones keep getting excluded one after the other at LHC, but there is always the "next most probable model" to go on with (and conferences will always proclaim that "susy is just around the corner").

  • $\begingroup$ I'm not sure if it is true to say the conferences will always proclaim that susy is just around the corner. I suspect that conferences in this area are a bit more serious than that. $\endgroup$ – Andrew Steane Dec 2 '19 at 11:26
  • $\begingroup$ @AndrewSteane in all seriousness, it's actually been like this for the last couple of decades; it's only in the last two years that the momentum started decreasing. $\endgroup$ – Helen - down with PCorrectness Dec 3 '19 at 12:44

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