  While the bino-dominated lightest neutralino of the minimal supersymmetric
Standard Model (MSSM) is an interesting and widely-studied candidate of the
dark matter, the p-wave suppression of its annihilation cross section requires
fine-tunings of the MSSM spectra to be consistent with WMAP observations. We
propose pseudo-Dirac bino that arises in theories with D-type
supersymmetry-breaking as an intriguing alternative candidate of dark matter.
The pseudo-Dirac nature of the bino gives a natural mechanism of enhanced
co-annihilation because these two states are degenerate in the absence of
electroweak symmetry breaking. In addition, the lightest state can be
consistent with limits of direct detection experiments because of the lack of
vector interactions, as with the case of the MSSM bino.
