"Arkani-Hamed and Dimopoulos ... have even shown how it is possible to keep the good features of supersymmetry, such as a more accurate convergence of the SU(3) × SU(2) × U(1) couplings to a single value, and the presence of candidates for dark matter WIMPs. The idea of this “split supersymmetry” is that, although supersymmetry is broken at some very high energy, the gauginos and higgsinos are kept light by a chiral symmetry. [An additional discrete symmetry is needed to prevent lepton-number violation in higgsino-lepton mixing, and to keep the lightest supersymmetric particle stable.]"