Relic Density of Neutralino Dark Matter in Supergravity Models

We calculate the relic density χ01 h2) of neutralino dark matter in supergravity models with radiative electroweak symmetry breaking for values of the Higgs sector parameter tan β ≡ v2/v1 between the two infrared fixed points of the top quark Yukawa coupling, tan β ' 1.8 and tanβ ' 56. For tanβ ∼ 10, the CP-odd Higgs pseudoscalar (A0) and the heavier CP-even Higgs scalar (H0) are much heavier than the lightest neutralino (χ1), and the annihilation cross section of χ1 pairs is significantly enhanced only in the vicinity of the lighter CP-even Higgs boson (h0) and the Z boson poles. For tan β ∼ 35, mA and mH become comparable to χ01 , and the neutralino annihilation cross section can be significantly enhanced by the poles of the H0 and the A0 as well. For a cosmologically interesting relic density, 0.1 ∼ χ01 2 < ∼ 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. Typeset using REVTEX