I am actually not 100% sure to follow the question. I will try to answer it by dissecting it. Feel free to interrupt my answer as soon as there is something that is unclear.
First of all, I am only focusing on the matter part of the energy budget of the universe. We thus ignore dark energy.
There, we have more or less 85% of dark matter and 15% of standard matter. The 85% of dark matter are then made of the only dark matter particle included in all supersymmetric partners. All the other supersymmetric partners being unstable particles (they decay into dark matter), they are not there anymore in our universe today. Whereas they were present in the early universe, they have indeed all decayed since then.
Please let me know whether this clarifies. Cheers!
Yes, that indeed clarifies it very well. The confusion when I was reading was at this point:
Somehow I thought IT alone decays into dark matter.But this cleared it up pretty well:
👍
Ah OK I see the issue and where the confusion came from.
Dark matter is in fact one particle from the full set of supersymmetric partners. It has to be the lightest one, or in other words the only one that can be stable. Any supersymmetric particle can always decay in a lighter supersymmetric particle, which is thus impossible for the lightest state.
Yup, all clear now. Thanks :)