Exact Cross Sections for the Neutralino WIMP Pair-Annihilation
  We derive a full set of exact, analytic expressions for the annihilation of the lightest neutralino pairs into all two-body tree-level final states in the framework of minimal supersymmetry. We make no simplifying assumptions about the neutralino nor about sfermion masses and mixings other than the absence of explicit CP--violating terms. The expressions should be particularly useful in computing the neutralino WIMP relic abundance without the usual approximation of partial wave expansion. 
Takeshi Nihei, Leszek Roszkowski, Roberto Ruiz de Austri