Effect of a late decaying scalar on the neutralino relic density

If the energy density of the Universe before nucleosynthesis is dominated by a scalar field phi that decays and reheats the plasma to a temperature T-RH smaller than the standard neutralino freeze-out temperature, the neutralino relic density differs from its standard value. In this case, the relic density depends on two additional parameters: T-RH, and the number of neutralinos produced per phi decay per unit mass of the phi field. In this paper, we numerically study the neutralino relic density as a function of these reheating parameters within minimal supersymmetric standard models and show that the dark matter constraint can almost always be satisfied.