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 φ that decays and reheats the plasma to a temperature TRH 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: TRH, and the number of neutralinos produced per φ decay per unit mass of the φ 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.