Theorists advanced supersymmetry, nicknamed SUSY, to deal with several nagging issues the standard model left unanswered, such as why some elemental particles have mass, how electromagnetism and the strong and weak nuclear forces might once have tied together and, possibly, what dark matter is made of. It also established a tantalizing relationship between the quarks and leptons that make up matter and the bosons that mediate their interactions. Like the baryons mentioned earlier, leptons (such as electrons) belong to a group of subatomic particles called fermions which have opposing quantum properties to bosons. Yet, according to SUSY, every fermion has a corresponding boson, and vice versa, and each particle can transform into its counterpart [sources: CERN; Siegried].
If true, SUSY would mean that the two elemental particle types (fermions and bosons) are merely two sides of the same coin; it would remove certain runaway infinite quantities that crop up in the mathematics by letting corresponding particles cancel out; and it would make room for gravity -- a glaring omission in the standard model -- because fermion-boson and boson-fermion conversions might involve gravitons, the long-theorized gravity force-carriers.
Physicists hoped that the LHC would either find evidence to support SUSY or reveal deeper problems that would point toward new theoretical and experimental territory. So far, neither appears to have happened, but don't count supersymmetry out just yet. SUSY exists in many versions, each linked to particular assumptions; the LHC has merely sifted out some of the most elegant and likely varieties.