Relic Density of Neutralino Dark Matter in Supergravity Models

Abstract

We calculate the relic density ($\hat{I}{\text{c◯}}_{\ddot{I}{‡}_1^0}{h}^2$) of neutralino dark matter in supergravity models with radiative electroweak symmetry breaking, for values of the Higgs sector parameter $\tan {\hat{I}}^2\equiv v_2/v_1$ between the two infrared fixed points of the top quark Yukawa coupling, $\tan {\hat{I}}^2\simeq 1.8$ and $\tan {\hat{I}}^2\simeq 56$. For $\tanβ\alt 10$, the CP-odd Higgs pseudoscalar ($A^0$) and the heavier CP-even Higgs scalar ($H^0$) are much heavier than the lightest neutralino ($\ddot{I}{‡}_1^0$), and the annihilation cross section of $\ddot{I}{‡}_1^0$ pairs is significantly enhanced only in the vicinity of the lighter CP-even Higgs boson ($h^0$) and the $Z$ boson poles. For $\tanβ\agt 40$, $m_A$ and $m_H$ become comparable to $2m_{\ddot{I}{‡}_1^0}$, and the neutralino annihilation cross section can be significantly enhanced by the poles of the $H^0$ and the $A^0$ as well. For a cosmologically interesting relic density, $0.1 \alt Ω_{χ^0_1} h^2 \alt 0.5$, we find that the supergravity parameter space is tightly constrained. The mass spectra for supersymmetric particles are presented for unification mass parameters in the cosmologically interesting region.

REVTEX, 27 pages, 15 eps figures, to be published in Physical Review D