Big bang nucleosynthesis constrains the total annihilation cross section   of neutralino dark matter
  Assuming the lightest neutralino forms dark matter, we study its residual annihilation after freeze-out at the early universe. If taking place after the big bang nucleosynthesis (BBN) the annihilation products, especially at the hadronic modes, may cause nonthermal nuclear reaction and change the prediction of the primordial abundance of light elements in the standard BBN scenario. We therefore put constraints on the neutralino annihilation cross section. These constraints are free of the uncertainties of the dark matter profile today suffered by direct or indirect detection of dark matter. We find the constraints by BBN is important, especially when taking large $\tan\beta$. If the light element abundances can be determined with higher precision in the future the constraint will become very strong, so that a majority of the parameter space allowed by the relic density requirement may be excluded. 
Xiao-Jun Bi