Superpartners are the bosinos: photinos, gauginos, zinos, winos (all partners of bosons); and the sfermions: selectrons, squarks (sleptons and shadrons, all partners of fermions).
I used to think they were all neutral- no charges. But from reading Lisa Randalls book, Warped Passages, I learned that they all sfermions have the same electric and color charge as its partner.
So why are they not easily detected in nature. She says they must have the exact same properties as well. That is because when they are created as virtual particles, i.e., fermions and anti-fermions have opposite charge and sferions and anti-sfermions have opposite charge, the set of four different virtual particles cancel each other out. Therefore they must also have equal masses. That is, the cancellation happens in the creation of virtual particles and is happening all the time and not just in the Big Bang as I previously thought.
But the fact that we cannot detect sfermions says something very significant about the Big Bang. Contrary to ordinary particles where slightly more particles than anti-particles are created at very high temperatures, exactly equal numbers of sfermions and anti-sfermions are created. Then when the universe expanded and the temperature dropped, all sfermions were annihilated by anti-sfermions; whereas, in the fermion case, a few fermions were left over after annihilation. The left over fermions became the physical world we live in including all that we can see.
The same is likely true for the bosinos. So the hunt for the photino, the lightest of the supersymmetric partners, is likely to be fruitless. Supersymmetry is only manisfested in the creation of virtual particles.
Randall's book is recommended for other reasons. For the first time I learned that epistomology runs the world rather than onotology. Philosophical terms, epi.. is the study of what we can measure or know whereas ono.. is the study of what actually exists. What Lisa taught me is that everything that we cannot measure is allowed to exist. For example, the uncertainty principle says that we cannot know the energy of a particle using a brief measurement. That means that all particles of that energy or less are allowed to exist for such a brief period of time. These are the virtual particles. I of course knew that virtual particles could exist. But I never realized that there existence meant that epi.. determines ono.. That is, ono.. includes everything that epi.. does not expressly forbid. Of course, now with supersymmetric cancellation of virtual particle effects, most of what is not forbidden is cancelled out. So in some sense, effectively nothing exists beyond epi..
Another thing Lisa taught me is how the Higgs mechanism works. The Higgs field is the mechanism that gives mass to all ferminos and bosons except the photon. I have read mention of this mechanism over and over, but never read an explanation of how it might work. Of course, nobody knows for sure. But the simplest explanation is that the Higgs field spreads charge uniformly throughout the universe. Then the fields produced by any particle cannot propagate pass the Higgs charge. The limited extent of a particles field then means that the particle has mass. There is no Higgs charge that can stop a photon, which can propagate throughout the universe. Therefore the photon is massless. Higgs charges only exist below 250GEV. So all particles are massless above 250 GEV, as has been experimentally verified every time.
And I have not finished the book yet.