Neutralino with the right cold dark matter abundance in (almost) any supersymmetric model

We consider nonstandard cosmological models in which the late decay of a scalar field $\varphi$ reheats the Universe to a low reheating temperature, between 5 MeV and the standard freeze-out temperature of neutralinos of mass $m_{\chi }$. We point out that in these models all neutralinos with standard density ${\Omega }_{\mathrm{std}}\gtrsim {10}^{-5}(100\mathrm{GeV}/m_{\chi })$ can have the density of cold dark matter, provided the right combination of the following two parameters can be achieved in the high-energy theory: the reheating temperature, and the ratio of the number of neutralinos produced per $\varphi$ decay over the $\varphi$ field mass. We present the ranges of these parameters where a combination of thermal and nonthermal neutralino production leads to the desired density, as functions of ${\Omega }_{\mathrm{std}}$ and $m_{\chi }$.

Figure 1

Neutralino density ${\Omega }_{\chi }{h}^2$ as a function of the reheating temperature $T_{\mathrm{RH}}$ for illustrative values of the ratio $\eta =b(100\mathrm{TeV}/m_{\varphi })$ (the number of neutralinos produced per unit of energy released in $\varphi$ decay, in units of $(100\mathrm{TeV}{)}^{-1}$). The curves are insensitive to the initial conditions, i.e. to the value $H_I$ of the Hubble parameter at the beginning of the $\varphi$ dominated epoch.